nQueens (count solutions).c

#include <stdio.h>
#include <stdlib.h>

int nQueensAll(int** board, int N, int col);
int isSafe(int** board,int N, int row, int col);
void printSolution(int** board, int N);
int count = 0;

int main()
{
    int **board;
    int BSize;

    int i,j;

    printf("Enter the size of chessBoard:\n");
    scanf("%d",&BSize);

    board = (int **)malloc(BSize*sizeof(int *));
    for(i=0;i<BSize;i++)
        board[i] = (int *)malloc(BSize*sizeof(int));

    for(i=0;i<BSize;i++)
       for(j=0;j<BSize;j++)
           board[i][j] = 0;

    nQueensAll(board, BSize, 0);
    if (count == 0)
    	printf("Solution does not exist");
    else
    	printf("There are total %d solutions",count);

    return 0;
}


int nQueensAll(int** board, int BSize, int col)
{
     // write your code here
    if (col == BSize)
    {
        count++;
        return 1;
    }

    int i;
    int found =0;
    for (i = 0; i < BSize; i++) { // check row by row in the (col)^th column
        // Safe to place
        if (isSafe(board,BSize, i, col)) {
            // Place a queen in this square
            board[i][col] = 1;

           // recursive the next column placement
            found = nQueensAll(board, BSize, col+1);

            //Delete the queen - Backtrack
            board[i][col] = 0;
        }
    }

    return found;
}

//Safe checking
int isSafe(int** board,int BSize, int row, int col)
{
    int i, j;

    // Horicatal check
    for (i = 0; i < col; i++)
        if (board[row][i])
            return 0;

    // Upper left diagonal check
    for (i = row, j = col; i >= 0 && j >= 0; i--, j--)
        if (board[i][j])
            return 0;

    // Lower left diagonal check
    for (i = row, j = col; j >= 0 && i < BSize; i++, j--)
        if (board[i][j])
            return 0;

    return 1;
}

void printSolution(int** board, int BSize)
{
    int i,j;
    for (i = 0; i < BSize; i++) {
        for (j = 0; j < BSize; j++){
            if(board[i][j]==1)
                printf(" Q ");
            else
                printf(" + ");
        }
        printf("\n");
    }
    printf("\n");
}