C++ Example of Dungeon-Building Algorithm

Version 1

(Translated to C++ by MindControlDx)

#include <iostream>
#include <string>
#include <cstdlib>
#include <cstdio>
#include <ctime>

class Dungeon
{
    int xmax;
    int ymax;

    int xsize;
    int ysize;

    int objects;

    int chanceRoom;
    int chanceCorridor;

    int* dungeon_map;

    long oldseed;

    enum
    {
        tileUnused = 0,
        tileDirtWall,
        tileDirtFloor,
        tileStoneWall,
        tileCorridor,
        tileDoor,
        tileUpStairs,
        tileDownStairs,
        tileChest
    };

    std::string msgXSize;
    std::string msgYSize;
    std::string msgMaxObjects;
    std::string msgNumObjects;
    std::string msgHelp;
    std::string msgDetailedHelp;

    void setCell(int x, int y, int celltype)
    {
        dungeon_map[x + xsize * y] = celltype;
    }
    int getCell(int x, int y)
    {
        return dungeon_map[x + xsize * y];
    }

    int getRand(int min, int max)
    {
        time_t seed;
        seed = time(NULL) + oldseed;
        oldseed = seed;

        srand(seed);

        int n = max - min + 1;
        int i = rand() % n;

        if(i < 0)
            i = -i;

        return min + i;
    }

    bool makeCorridor(int x, int y, int lenght, int direction)
    {
        int len = getRand(2, lenght);
        int floor = tileCorridor;
        int dir = 0;
        if(direction > 0 && direction < 4) dir = direction;

        int xtemp = 0;
        int ytemp = 0;

        switch(dir)
        {
            case 0:
            {
                if(x < 0 || x > xsize) return false;
                else xtemp = x;

                for(ytemp = y; ytemp > (y-len); ytemp--)
                {
                    if(ytemp < 0 || ytemp > ysize) return false;
                    if(getCell(xtemp, ytemp) != tileUnused) return false;
                }

                for(ytemp = y; ytemp > (y - len); ytemp--)
                {
                    setCell(xtemp, ytemp, floor);
                }
                break;

            }
            case 1:
            {
                if(y < 0 || y > ysize) return false;
                else ytemp = y;

                for(xtemp = x; xtemp < (x + len); xtemp++)
                {
                    if(xtemp < 0 || xtemp > xsize) return false;
                    if(getCell(xtemp, ytemp) != tileUnused) return false;
                }

                for(xtemp = x; xtemp < (x + len); xtemp++)
                {
                    setCell(xtemp, ytemp, floor);
                }
                break;
            }
            case 2:
            {
                if(x < 0 || x > xsize) return false;
                else xtemp = x;

                for(ytemp = y; ytemp < (y + len); ytemp++)
                {
                    if(ytemp < 0 || ytemp > ysize) return false;
                    if(getCell(xtemp, ytemp) != tileUnused) return false;
                }
                for (ytemp = y; ytemp < (y+len); ytemp++){
                    setCell(xtemp, ytemp, floor);
                }
			break;
            }
            case 3:
            {
                if (ytemp < 0 || ytemp > ysize) return false;
                else ytemp = y;

                for (xtemp = x; xtemp > (x-len); xtemp--){
                    if (xtemp < 0 || xtemp > xsize) return false;
                    if (getCell(xtemp, ytemp) != tileUnused) return false;
                }

                for (xtemp = x; xtemp > (x-len); xtemp--){
                    setCell(xtemp, ytemp, floor);
                }
                break;
            }
		}
		//woot, we're still here! let's tell the other guys we're done!!
		return true;
	}
	bool makeRoom(int x, int y, int xlength, int ylength, int direction){
		//define the dimensions of the room, it should be at least 4x4 tiles (2x2 for walking on, the rest is walls)
		int xlen = getRand(4, xlength);
		int ylen = getRand(4, ylength);
		//the tile type it's going to be filled with
		int floor = tileDirtFloor; //jordgolv..
		int wall = tileDirtWall; //jordv????gg
		//choose the way it's pointing at
		int dir = 0;
		if (direction > 0 && direction < 4) dir = direction;

		switch(dir){
		case 0:
		//north
			//Check if there's enough space left for it
			for (int ytemp = y; ytemp > (y-ylen); ytemp--){
				if (ytemp < 0 || ytemp > ysize) return false;
				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){
					if (xtemp < 0 || xtemp > xsize) return false;
					if (getCell(xtemp, ytemp) != tileUnused) return false; //no space left...
				}
			}

			//we're still here, build
			for (int ytemp = y; ytemp > (y-ylen); ytemp--){
				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){
					//start with the walls
					if (xtemp == (x-xlen/2)) setCell(xtemp, ytemp, wall);
					else if (xtemp == (x+(xlen-1)/2)) setCell(xtemp, ytemp, wall);
					else if (ytemp == y) setCell(xtemp, ytemp, wall);
					else if (ytemp == (y-ylen+1)) setCell(xtemp, ytemp, wall);
					//and then fill with the floor
					else setCell(xtemp, ytemp, floor);
				}
			}
			break;
		case 1:
		//east
			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){
				if (ytemp < 0 || ytemp > ysize) return false;
				for (int xtemp = x; xtemp < (x+xlen); xtemp++){
					if (xtemp < 0 || xtemp > xsize) return false;
					if (getCell(xtemp, ytemp) != tileUnused) return false;
				}
			}

			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){
				for (int xtemp = x; xtemp < (x+xlen); xtemp++){

					if (xtemp == x) setCell(xtemp, ytemp, wall);
					else if (xtemp == (x+xlen-1)) setCell(xtemp, ytemp, wall);
					else if (ytemp == (y-ylen/2)) setCell(xtemp, ytemp, wall);
					else if (ytemp == (y+(ylen-1)/2)) setCell(xtemp, ytemp, wall);

					else setCell(xtemp, ytemp, floor);
				}
			}
			break;
		case 2:
		//south
			for (int ytemp = y; ytemp < (y+ylen); ytemp++){
				if (ytemp < 0 || ytemp > ysize) return false;
				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){
					if (xtemp < 0 || xtemp > xsize) return false;
					if (getCell(xtemp, ytemp) != tileUnused) return false;
				}
			}

			for (int ytemp = y; ytemp < (y+ylen); ytemp++){
				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){

					if (xtemp == (x-xlen/2)) setCell(xtemp, ytemp, wall);
					else if (xtemp == (x+(xlen-1)/2)) setCell(xtemp, ytemp, wall);
					else if (ytemp == y) setCell(xtemp, ytemp, wall);
					else if (ytemp == (y+ylen-1)) setCell(xtemp, ytemp, wall);

					else setCell(xtemp, ytemp, floor);
				}
			}
			break;
		case 3:
		//west
			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){
				if (ytemp < 0 || ytemp > ysize) return false;
				for (int xtemp = x; xtemp > (x-xlen); xtemp--){
					if (xtemp < 0 || xtemp > xsize) return false;
					if (getCell(xtemp, ytemp) != tileUnused) return false;
				}
			}

			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){
				for (int xtemp = x; xtemp > (x-xlen); xtemp--){

					if (xtemp == x) setCell(xtemp, ytemp, wall);
					else if (xtemp == (x-xlen+1)) setCell(xtemp, ytemp, wall);
					else if (ytemp == (y-ylen/2)) setCell(xtemp, ytemp, wall);
					else if (ytemp == (y+(ylen-1)/2)) setCell(xtemp, ytemp, wall);

					else setCell(xtemp, ytemp, floor);
				}
			}
			break;
		}

		//yay, all done
		return true;
	}
	void showDungeon(){
		for (int y = 0; y < ysize; y++){
			for (int x = 0; x < xsize; x++){
				//System.out.print(getCell(x, y));
				switch(getCell(x, y)){
				case tileUnused:
					printf(" ");
					break;
				case tileDirtWall:
					printf("#");
					break;
				case tileDirtFloor:
					printf(".");
					break;
				case tileStoneWall:
					printf("X");
					break;
				case tileCorridor:
					printf(".");
					break;
				case tileDoor:
					printf("+");
					break;
				case tileUpStairs:
					printf("<");
					break;
				case tileDownStairs:
					printf(">");
					break;
				case tileChest:
					printf("*");
					break;
				};
			}
			//if (xsize <= xmax) printf("\n");
		}
	}
	bool createDungeon(int inx, int iny, int inobj){
		if (inobj < 1) objects = 10;
		else objects = inobj;

		//justera kartans storlek, om den ????r st????rre eller mindre ????n "gr????nserna"
		//adjust the size of the map, if it's smaller or bigger than the limits
		if (inx < 3) xsize = 3;
		else if (inx > xmax) xsize = xmax;
		else xsize = inx;

		if (iny < 3) ysize = 3;
		else if (iny > ymax) ysize = ymax;
		else ysize = iny;

		//printf("%s %d\n", msgXSize.c_str(), xsize);
		//printf("%s %d\n", msgYSize.c_str(),  + ysize);
		//printf("%s %d\n", msgMaxObjects.c_str(), objects);

		//redefine the map var, so it's adjusted to our new map size
		dungeon_map = new int[xsize * ysize];

		//start with making the "standard stuff" on the map
		for (int y = 0; y < ysize; y++){
			for (int x = 0; x < xsize; x++){
				//ie, making the borders of unwalkable walls
				if (y == 0) setCell(x, y, tileStoneWall);
				else if (y == ysize-1) setCell(x, y, tileStoneWall);
				else if (x == 0) setCell(x, y, tileStoneWall);
				else if (x == xsize-1) setCell(x, y, tileStoneWall);

				//and fill the rest with dirt
				else setCell(x, y, tileUnused);
			}
		}

		/*******************************************************************************
		And now the code of the random-map-generation-algorithm begins!
		*******************************************************************************/

		//start with making a room in the middle, which we can start building upon
		makeRoom(xsize/2, ysize/2, 8, 6, getRand(0,3)); //getrand saken f????r att slumpa fram riktning p?? rummet

		//keep count of the number of "objects" we've made
		int currentFeatures = 1; //+1 for the first room we just made

		//then we sart the main loop
		for (int countingTries = 0; countingTries < 1000; countingTries++){
			//check if we've reached our quota
			if (currentFeatures == objects){
				break;
			}

			//start with a random wall
			int newx = 0;
			int xmod = 0;
			int newy = 0;
			int ymod = 0;
			int validTile = -1;
			//1000 chances to find a suitable object (room or corridor)..
			//(yea, i know it's kinda ugly with a for-loop... -_-')
			for (int testing = 0; testing < 1000; testing++){
				newx = getRand(1, xsize-1);
				newy = getRand(1, ysize-1);
				validTile = -1;
				//System.out.println("tempx: " + newx + "\ttempy: " + newy);
				if (getCell(newx, newy) == tileDirtWall || getCell(newx, newy) == tileCorridor){
					//check if we can reach the place
					if (getCell(newx, newy+1) == tileDirtFloor || getCell(newx, newy+1) == tileCorridor){
						validTile = 0; //
						xmod = 0;
						ymod = -1;
					}
					else if (getCell(newx-1, newy) == tileDirtFloor || getCell(newx-1, newy) == tileCorridor){
						validTile = 1; //
						xmod = +1;
						ymod = 0;
					}
					else if (getCell(newx, newy-1) == tileDirtFloor || getCell(newx, newy-1) == tileCorridor){
						validTile = 2; //
						xmod = 0;
						ymod = +1;
					}
					else if (getCell(newx+1, newy) == tileDirtFloor || getCell(newx+1, newy) == tileCorridor){
						validTile = 3; //
						xmod = -1;
						ymod = 0;
					}

					//check that we haven't got another door nearby, so we won't get alot of openings besides
					//each other
					if (validTile > -1){
						if (getCell(newx, newy+1) == tileDoor) //north
							validTile = -1;
						else if (getCell(newx-1, newy) == tileDoor)//east
							validTile = -1;
						else if (getCell(newx, newy-1) == tileDoor)//south
							validTile = -1;
						else if (getCell(newx+1, newy) == tileDoor)//west
							validTile = -1;
					}

					//if we can, jump out of the loop and continue with the rest
					if (validTile > -1) break;
				}
			}
			if (validTile > -1){
				//choose what to build now at our newly found place, and at what direction
				int feature = getRand(0, 100);
				if (feature <= chanceRoom){ //a new room
					if (makeRoom((newx+xmod), (newy+ymod), 8, 6, validTile)){
						currentFeatures++; //add to our quota

						//then we mark the wall opening with a door
						setCell(newx, newy, tileDoor);

						//clean up infront of the door so we can reach it
						setCell((newx+xmod), (newy+ymod), tileDirtFloor);
					}
				}
				else if (feature >= chanceRoom){ //new corridor
					if (makeCorridor((newx+xmod), (newy+ymod), 6, validTile)){
						//same thing here, add to the quota and a door
						currentFeatures++;

						setCell(newx, newy, tileDoor);
					}
				}
			}
		}


		/*******************************************************************************
		All done with the building, let's finish this one off
		*******************************************************************************/

		//sprinkle out the bonusstuff (stairs, chests etc.) over the map
		int newx = 0;
		int newy = 0;
		int ways = 0; //from how many directions we can reach the random spot from
		int state = 0; //the state the loop is in, start with the stairs
		while (state != 10){
			for (int testing = 0; testing < 1000; testing++){
				newx = getRand(1, xsize-1);
				newy = getRand(1, ysize-2); //cheap bugfix, pulls down newy to 0<y<24, from 0<y<25

				//System.out.println("x: " + newx + "\ty: " + newy);
				ways = 4; //the lower the better

				//check if we can reach the spot
				if (getCell(newx, newy+1) == tileDirtFloor || getCell(newx, newy+1) == tileCorridor){
				//north
					if (getCell(newx, newy+1) != tileDoor)
					ways--;
				}
				if (getCell(newx-1, newy) == tileDirtFloor || getCell(newx-1, newy) == tileCorridor){
				//east
					if (getCell(newx-1, newy) != tileDoor)
					ways--;
				}
				if (getCell(newx, newy-1) == tileDirtFloor || getCell(newx, newy-1) == tileCorridor){
				//south
					if (getCell(newx, newy-1) != tileDoor)
					ways--;
				}
				if (getCell(newx+1, newy) == tileDirtFloor || getCell(newx+1, newy) == tileCorridor){
				//west
					if (getCell(newx+1, newy) != tileDoor)
					ways--;
				}

				if (state == 0){
					if (ways == 0){
					//we're in state 0, let's place a "upstairs" thing
						setCell(newx, newy, tileUpStairs);
						state = 1;
						break;
					}
				}
				else if (state == 1){
					if (ways == 0){
					//state 1, place a "downstairs"
						setCell(newx, newy, tileDownStairs);
						state = 10;
						break;
					}
				}
			}
		}


		//all done with the map generation, tell the user about it and finish
		//printf("%s %d\n",msgNumObjects.c_str(), currentFeatures);

		return true;
	}

    void cmain()
    {
        int x = 80;
        int y = 25;
        int dungeon_objects = 100;
        dungeon_map = new int[x * y];
        for(;;)
        {
            if(createDungeon(x, y, dungeon_objects))
            showDungeon();
            std::cin.get();
        }
    }
public:
    Dungeon()
    {
        xmax = 80;
        ymax = 25;

        xsize = 0;
        ysize = 0;

        objects = 0;

        chanceRoom = 75;
        chanceCorridor = 25;

        msgXSize = "X size of dungeon: \t";
        msgYSize = "Y size of dungeon: \t";
        msgMaxObjects = "max # of objects: \t";
        msgNumObjects = "# of objects made: \t";
        msgHelp = "";
        msgDetailedHelp = "";

        cmain();
    }
};

int main()
{
    Dungeon d;
    
    return EXIT_SUCCESS;
}

Version 2

Cleaned up and modernised a little by netherh.

(Use C++11 random number generator. Common functionality abstracted. Simple Map class added.)

#include <iostream>
#include <string>
#include <random>
#include <cassert>

enum class Tile
{
	Unused,
	DirtWall,
	DirtFloor,
	Corridor,
	Door,
	UpStairs,
	DownStairs
};

enum class Direction
{
	North, South, East, West,
};

class Map
{
public:

	Map():
		xSize(0), ySize(0),
		data() { }

	Map(int x, int y, Tile value = Tile::Unused):
		xSize(x), ySize(y),
		data(x * y, value) { }
	
	void SetCell(int x, int y, Tile celltype)
	{
		assert(IsXInBounds(x));
		assert(IsYInBounds(y));

		data[x + xSize * y] = celltype;
	}

	Tile GetCell(int x, int y) const
	{
		assert(IsXInBounds(x));
		assert(IsYInBounds(y));

		return data[x + xSize * y];
	}
	
	void SetCells(int xStart, int yStart, int xEnd, int yEnd, Tile cellType)
	{
		assert(IsXInBounds(xStart) && IsXInBounds(xEnd));
		assert(IsYInBounds(yStart) && IsYInBounds(yEnd));

		assert(xStart <= xEnd);
		assert(yStart <= yEnd);

		for (auto y = yStart; y != yEnd + 1; ++y)
			for (auto x = xStart; x != xEnd + 1; ++x)
				SetCell(x, y, cellType);
	}
	
	bool IsXInBounds(int x) const
	{
		return x >= 0 && x < xSize;
	}

	bool IsYInBounds(int y) const
	{
		return y >= 0 && y < ySize;
	}

	bool IsAreaUnused(int xStart, int yStart, int xEnd, int yEnd)
	{
		assert(IsXInBounds(xStart) && IsXInBounds(xEnd));
		assert(IsYInBounds(yStart) && IsYInBounds(yEnd));

		assert(xStart <= xEnd);
		assert(yStart <= yEnd);
		
		for (auto y = yStart; y != yEnd + 1; ++y)
			for (auto x = xStart; x != xEnd + 1; ++x)
				if (GetCell(x, y) != Tile::Unused)
					return false;

		return true;
	}

	bool IsAdjacent(int x, int y, Tile tile)
	{
		assert(IsXInBounds(x - 1) && IsXInBounds(x + 1));
		assert(IsYInBounds(y - 1) && IsYInBounds(y + 1));

		return 
			GetCell(x - 1, y) == tile || GetCell(x + 1, y) == tile ||
			GetCell(x, y - 1) == tile || GetCell(x, y + 1) == tile;
	}

	void Print() const
	{
		// TODO: proper ostream iterator.
		// TODO: proper lookup of character from enum.

		for (auto y = 0; y != ySize; y++)
		{
			for (auto x = 0; x != xSize; x++)
			{
				switch(GetCell(x, y))
				{
				case Tile::Unused:
					std::cout << " ";
					break;
				case Tile::DirtWall:
					std::cout << "#";
					break;
				case Tile::DirtFloor:
					std::cout << ".";
					break;
				case Tile::Corridor:
					std::cout << ".";
					break;
				case Tile::Door:
					std::cout << "+";
					break;
				case Tile::UpStairs:
					std::cout << "<";
					break;
				case Tile::DownStairs:
					std::cout << ">";
					break;
				};
			}

			std::cout << std::endl;
		}

		std::cout << std::endl;
	}

private:

	int xSize, ySize;

	std::vector<Tile> data;
};

class DungeonGenerator
{
public:
	
	int Seed;

	int XSize, YSize;
 
	int MaxFeatures;
 
	int ChanceRoom, ChanceCorridor;

	DungeonGenerator():
		Seed(std::random_device()()),
		XSize(80), YSize(25),
		MaxFeatures(100),
		ChanceRoom(75), ChanceCorridor(25) { }

	Map Generate()
	{
		// TODO: proper input validation.
		assert(MaxFeatures > 0 && MaxFeatures <= 100);
		assert(XSize > 3 && XSize <= 80);
		assert(YSize > 3 && YSize <= 25);

		auto rng = RngT(Seed);
		auto map = Map(XSize, YSize, Tile::Unused);

		MakeDungeon(map, rng);

		return map;
	}

private:

	typedef std::mt19937 RngT;
	
	int GetRandomInt(RngT& rng, int min, int max) const
	{
		return std::uniform_int_distribution<int>(min, max)(rng);
	}

	Direction GetRandomDirection(RngT& rng) const
	{
		return Direction(std::uniform_int_distribution<int>(0, 3)(rng));
	}
	
	bool MakeCorridor(Map& map, RngT& rng, int x, int y, int maxLength, Direction direction) const
	{
		assert(x >= 0 && x < XSize);
		assert(y >= 0 && y < YSize);

		assert(maxLength > 0 && maxLength <= std::max(XSize, YSize));

		auto length = GetRandomInt(rng, 2, maxLength);

		auto xStart = x;
		auto yStart = y;

		auto xEnd = x;
		auto yEnd = y;

		if (direction == Direction::North)
			yStart = y - length;
		else if (direction == Direction::East)
			xEnd = x + length;
		else if (direction == Direction::South)
			yEnd = y + length;
		else if (direction == Direction::West)
			xStart = x - length;

		if (!map.IsXInBounds(xStart) || !map.IsXInBounds(xEnd) || !map.IsYInBounds(yStart) || !map.IsYInBounds(yEnd))
			return false;
		
		if (!map.IsAreaUnused(xStart, yStart, xEnd, yEnd))
			return false;

		map.SetCells(xStart, yStart, xEnd, yEnd, Tile::Corridor);

		//std::cout << "Corridor: ( " << xStart << ", " << yStart << " ) to ( " << xEnd << ", " << yEnd << " )" << std::endl;

		return true;
	}

	bool MakeRoom(Map& map, RngT& rng, int x, int y, int xMaxLength, int yMaxLength, Direction direction) const
	{
		// Minimum room size of 4x4 tiles (2x2 for walking on, the rest is walls)
		auto xLength = GetRandomInt(rng, 4, xMaxLength);
		auto yLength = GetRandomInt(rng, 4, yMaxLength);

		auto xStart = x;
		auto yStart = y;

		auto xEnd = x;
		auto yEnd = y;
 
		if (direction == Direction::North)
		{
			yStart = y - yLength;
			xStart = x - xLength / 2;
			xEnd = x + (xLength + 1) / 2;
		}
		else if (direction == Direction::East)
		{
			yStart = y - yLength / 2;
			yEnd = y + (yLength + 1) / 2;
			xEnd = x + xLength;
		}
		else if (direction == Direction::South)
		{
			yEnd = y + yLength;
			xStart = x - xLength / 2;
			xEnd = x + (xLength + 1) / 2;
		}
		else if (direction == Direction::West)
		{
			yStart = y - yLength / 2;
			yEnd = y + (yLength + 1) / 2;
			xStart = x - xLength;
		}
		
		if (!map.IsXInBounds(xStart) || !map.IsXInBounds(xEnd) || !map.IsYInBounds(yStart) || !map.IsYInBounds(yEnd))
			return false;
		
		if (!map.IsAreaUnused(xStart, yStart, xEnd, yEnd))
			return false;

		map.SetCells(xStart, yStart, xEnd, yEnd, Tile::DirtWall);
		map.SetCells(xStart + 1, yStart + 1, xEnd - 1, yEnd - 1, Tile::DirtFloor);
		
		//std::cout << "Room: ( " << xStart << ", " << yStart << " ) to ( " << xEnd << ", " << yEnd << " )" << std::endl;

		return true;
	}

	bool MakeFeature(Map& map, RngT& rng, int x, int y, int xmod, int ymod, Direction direction) const
	{
		// Choose what to build
		auto chance = GetRandomInt(rng, 0, 100);

		if (chance <= ChanceRoom)
		{
			if (MakeRoom(map, rng, x + xmod, y + ymod, 8, 6, direction))
			{
				map.SetCell(x, y, Tile::Door);
					
				// Remove wall next to the door.
				map.SetCell(x + xmod, y + ymod, Tile::DirtFloor);
				
				return true;
			}

			return false;
		}
		else
		{
			if (MakeCorridor(map, rng, x + xmod, y + ymod, 6, direction))
			{
				map.SetCell(x, y, Tile::Door);

				return true;
			}

			return false;
		}
	}

	bool MakeFeature(Map& map, RngT& rng) const
	{
		auto tries = 0;
		auto maxTries = 1000;

		for( ; tries != maxTries; ++tries)
		{
			// Pick a random wall or corridor tile.
			// Make sure it has no adjacent doors (looks weird to have doors next to each other).
			// Find a direction from which it's reachable.
			// Attempt to make a feature (room or corridor) starting at this point.

			int x = GetRandomInt(rng, 1, XSize - 2);
			int y = GetRandomInt(rng, 1, YSize - 2);

			if (map.GetCell(x, y) != Tile::DirtWall && map.GetCell(x, y) != Tile::Corridor)
				continue;

			if (map.IsAdjacent(x, y, Tile::Door))
				continue;

			if (map.GetCell(x, y+1) == Tile::DirtFloor || map.GetCell(x, y+1) == Tile::Corridor)
			{
				if (MakeFeature(map, rng, x, y, 0, -1, Direction::North))
					return true;
			}
			else if (map.GetCell(x-1, y) == Tile::DirtFloor || map.GetCell(x-1, y) == Tile::Corridor)
			{
				if (MakeFeature(map, rng, x, y, 1, 0, Direction::East))
					return true;
			}
			else if (map.GetCell(x, y-1) == Tile::DirtFloor || map.GetCell(x, y-1) == Tile::Corridor)
			{
				if (MakeFeature(map, rng, x, y, 0, 1, Direction::South))
					return true;
			}
			else if (map.GetCell(x+1, y) == Tile::DirtFloor || map.GetCell(x+1, y) == Tile::Corridor)
			{
				if (MakeFeature(map, rng, x, y, -1, 0, Direction::West))
					return true;
			}
		}

		return false;
	}

	bool MakeStairs(Map& map, RngT& rng, Tile tile) const
	{
		auto tries = 0;
		auto maxTries = 10000;

		for ( ; tries != maxTries; ++tries)
		{
			int x = GetRandomInt(rng, 1, XSize - 2);
			int y = GetRandomInt(rng, 1, YSize - 2);
			
			if (!map.IsAdjacent(x, y, Tile::DirtFloor) && !map.IsAdjacent(x, y, Tile::Corridor))
				continue;

			if (map.IsAdjacent(x, y, Tile::Door))
				continue;

			map.SetCell(x, y, tile);

			return true;
		}

		return false;
	}

	bool MakeDungeon(Map& map, RngT& rng) const
	{
		// Make one room in the middle to start things off.
		MakeRoom(map, rng, XSize / 2, YSize / 2, 8, 6, GetRandomDirection(rng));
		
		for (auto features = 1; features != MaxFeatures; ++features)
		{
			if (!MakeFeature(map, rng))
			{
				std::cout << "Unable to place more features (placed " << features << ")." << std::endl;
				break;
			}
		}

		if (!MakeStairs(map, rng, Tile::UpStairs))
			std::cout << "Unable to place up stairs." << std::endl;

		if (!MakeStairs(map, rng, Tile::DownStairs))
			std::cout << "Unable to place down stairs." << std::endl;
		
		return true;
	}
	
};
 
int main()
{
	DungeonGenerator generator;

	auto map = generator.Generate();

	map.Print();
}

Version 3

Improved algorithm and cleaned up some code by underww

(This is derived from Version 2)

#include <random>
#include <vector>
#include <iostream>

namespace
{
	std::random_device rd;
	std::mt19937 mt(rd());

	int randomInt(int exclusiveMax)
	{
		std::uniform_int_distribution<> dist(0, exclusiveMax - 1);
		return dist(mt);
	}

	int randomInt(int min, int max) // inclusive min/max
	{
		std::uniform_int_distribution<> dist(0, max - min);
		return dist(mt) + min;
	}

	bool randomBool(double probability = 0.5)
	{
		std::bernoulli_distribution dist(probability);
		return dist(mt);
	}
}

struct Rect
{
	int x, y;
	int width, height;
};

class Dungeon
{
public:
	enum Tile
	{
		Unused		= ' ',
		Floor		= '.',
		Corridor	= ',',
		Wall		= '#',
		ClosedDoor	= '+',
		OpenDoor	= '-',
		UpStairs	= '<',
		DownStairs	= '>'
	};

	enum Direction
	{
		North,
		South,
		West,
		East,
		DirectionCount
	};

public:
	Dungeon(int width, int height)
		: _width(width)
		, _height(height)
		, _tiles(width * height, Unused)
		, _rooms()
		, _exits()
	{
	}

	void generate(int maxFeatures)
	{
		// place the first room in the center
		if (!makeRoom(_width / 2, _height / 2, static_cast<Direction>(randomInt(4), true)))
		{
			std::cout << "Unable to place the first room.\n";
			return;
		}

		// we already placed 1 feature (the first room)
		for (int i = 1; i < maxFeatures; ++i)
		{
			if (!createFeature())
			{
				std::cout << "Unable to place more features (placed " << i << ").\n";
				break;
			}
		}

		if (!placeObject(UpStairs))
		{
			std::cout << "Unable to place up stairs.\n";
			return;
		}

		if (!placeObject(DownStairs))
		{
			std::cout << "Unable to place down stairs.\n";
			return;
		}

		for (char& tile : _tiles)
		{
			if (tile == Unused)
				tile = '.';
			else if (tile == Floor || tile == Corridor)
				tile = ' ';
		}
	}

	void print()
	{
		for (int y = 0; y < _height; ++y)
		{
			for (int x = 0; x < _width; ++x)
				std::cout << getTile(x, y);

			std::cout << std::endl;
		}
	}

private:
	char getTile(int x, int y) const
	{
		if (x < 0 || y < 0 || x >= _width || y >= _height)
			return Unused;

		return _tiles[x + y * _width];
	}

	void setTile(int x, int y, char tile)
	{
		_tiles[x + y * _width] = tile;
	}

	bool createFeature()
	{
		for (int i = 0; i < 1000; ++i)
		{
			if (_exits.empty())
				break;

			// choose a random side of a random room or corridor
			int r = randomInt(_exits.size());
			int x = randomInt(_exits[r].x, _exits[r].x + _exits[r].width - 1);
			int y = randomInt(_exits[r].y, _exits[r].y + _exits[r].height - 1);

			// north, south, west, east
			for (int j = 0; j < DirectionCount; ++j)
			{
				if (createFeature(x, y, static_cast<Direction>(j)))
				{
					_exits.erase(_exits.begin() + r);
					return true;
				}
			}
		}

		return false;
	}

	bool createFeature(int x, int y, Direction dir)
	{
		static const int roomChance = 50; // corridorChance = 100 - roomChance

		int dx = 0;
		int dy = 0;

		if (dir == North)
			dy = 1;
		else if (dir == South)
			dy = -1;
		else if (dir == West)
			dx = 1;
		else if (dir == East)
			dx = -1;

		if (getTile(x + dx, y + dy) != Floor && getTile(x + dx, y + dy) != Corridor)
			return false;

		if (randomInt(100) < roomChance)
		{
			if (makeRoom(x, y, dir))
			{
				setTile(x, y, ClosedDoor);

				return true;
			}
		}

		else
		{
			if (makeCorridor(x, y, dir))
			{
				if (getTile(x + dx, y + dy) == Floor)
					setTile(x, y, ClosedDoor);
				else // don't place a door between corridors
					setTile(x, y, Corridor);

				return true;
			}
		}

		return false;
	}

	bool makeRoom(int x, int y, Direction dir, bool firstRoom = false)
	{
		static const int minRoomSize = 3;
		static const int maxRoomSize = 6;

		Rect room;
		room.width = randomInt(minRoomSize, maxRoomSize);
		room.height = randomInt(minRoomSize, maxRoomSize);

		if (dir == North)
		{
			room.x = x - room.width / 2;
			room.y = y - room.height;
		}

		else if (dir == South)
		{
			room.x = x - room.width / 2;
			room.y = y + 1;
		}

		else if (dir == West)
		{
			room.x = x - room.width;
			room.y = y - room.height / 2;
		}

		else if (dir == East)
		{
			room.x = x + 1;
			room.y = y - room.height / 2;
		}

		if (placeRect(room, Floor))
		{
			_rooms.emplace_back(room);

			if (dir != South || firstRoom) // north side
				_exits.emplace_back(Rect{ room.x, room.y - 1, room.width, 1 });
			if (dir != North || firstRoom) // south side
				_exits.emplace_back(Rect{ room.x, room.y + room.height, room.width, 1 });
			if (dir != East || firstRoom) // west side
				_exits.emplace_back(Rect{ room.x - 1, room.y, 1, room.height });
			if (dir != West || firstRoom) // east side
				_exits.emplace_back(Rect{ room.x + room.width, room.y, 1, room.height });

			return true;
		}

		return false;
	}

	bool makeCorridor(int x, int y, Direction dir)
	{
		static const int minCorridorLength = 3;
		static const int maxCorridorLength = 6;

		Rect corridor;
		corridor.x = x;
		corridor.y = y;

		if (randomBool()) // horizontal corridor
		{
			corridor.width = randomInt(minCorridorLength, maxCorridorLength);
			corridor.height = 1;

			if (dir == North)
			{
				corridor.y = y - 1;

				if (randomBool()) // west
					corridor.x = x - corridor.width + 1;
			}

			else if (dir == South)
			{
				corridor.y = y + 1;

				if (randomBool()) // west
					corridor.x = x - corridor.width + 1;
			}

			else if (dir == West)
				corridor.x = x - corridor.width;

			else if (dir == East)
				corridor.x = x + 1;
		}

		else // vertical corridor
		{
			corridor.width = 1;
			corridor.height = randomInt(minCorridorLength, maxCorridorLength);

			if (dir == North)
				corridor.y = y - corridor.height;

			else if (dir == South)
				corridor.y = y + 1;

			else if (dir == West)
			{
				corridor.x = x - 1;

				if (randomBool()) // north
					corridor.y = y - corridor.height + 1;
			}

			else if (dir == East)
			{
				corridor.x = x + 1;

				if (randomBool()) // north
					corridor.y = y - corridor.height + 1;
			}
		}

		if (placeRect(corridor, Corridor))
		{
			if (dir != South && corridor.width != 1) // north side
				_exits.emplace_back(Rect{ corridor.x, corridor.y - 1, corridor.width, 1 });
			if (dir != North && corridor.width != 1) // south side
				_exits.emplace_back(Rect{ corridor.x, corridor.y + corridor.height, corridor.width, 1 });
			if (dir != East && corridor.height != 1) // west side
				_exits.emplace_back(Rect{ corridor.x - 1, corridor.y, 1, corridor.height });
			if (dir != West && corridor.height != 1) // east side
				_exits.emplace_back(Rect{ corridor.x + corridor.width, corridor.y, 1, corridor.height });

			return true;
		}

		return false;
	}

	bool placeRect(const Rect& rect, char tile)
	{
		if (rect.x < 1 || rect.y < 1 || rect.x + rect.width >= _width - 1 || rect.y + rect.height >= _height - 1)
			return false;

		for (int y = rect.y; y < rect.y + rect.height; ++y)
			for (int x = rect.x; x < rect.x + rect.width; ++x)
			{
				if (getTile(x, y) != Unused)
					return false; // the area already used
			}

		for (int y = rect.y - 1; y < rect.y + rect.height + 1; ++y)
			for (int x = rect.x - 1; x < rect.x + rect.width + 1; ++x)
			{
				if (x == rect.x - 1 || y == rect.y - 1 || x == rect.x + rect.width || y == rect.y + rect.height)
					setTile(x, y, Wall);
				else
					setTile(x, y, tile);
			}

		return true;
	}

	bool placeObject(char tile)
	{
		if (_rooms.empty())
			return false;

		int r = randomInt(_rooms.size()); // choose a random room
		int x = randomInt(_rooms[r].x + 1, _rooms[r].x + _rooms[r].width - 2);
		int y = randomInt(_rooms[r].y + 1, _rooms[r].y + _rooms[r].height - 2);

		if (getTile(x, y) == Floor)
		{
			setTile(x, y, tile);

			// place one object in one room (optional)
			_rooms.erase(_rooms.begin() + r);

			return true;
		}

		return false;
	}

private:
	int _width, _height;
	std::vector<char> _tiles;
	std::vector<Rect> _rooms; // rooms for place stairs or monsters
	std::vector<Rect> _exits; // 4 sides of rooms or corridors
};

int main()
{
	Dungeon d(79, 24);
	d.generate(50);
	d.print();

	std::cout << "Press Enter to quit... ";
	std::cin.get();

	return 0;
}