define N 4

include

/ A utility function to print solution / void printSolution(int board[N][N]) { for (int i = 0; i < N; i++) { for (int j = 0; j < N; j++) printf(" %d ", board[i][j]); printf("\n"); } }

bool isSafe(int board[N][N], int row, int col) { int i, j;

for (i = 0; i < col; i++) if (board[row][i]) return false; for (i = row, j = col; i >= 0 && j >= 0; i--, j--) if (board[i][j]) return false;

for (i = row, j = col; j >= 0 && i < N; i++, j--) if (board[i][j]) return false;

return true; }

bool solveNQUtil(int board[N][N], int col) { / base case: If all queens are placed then return true / if (col >= N) return true; for (int i = 0; i < N; i++) { / Check if the queen can be placed on board[i][col] / if (isSafe(board, i, col)) {

    board[i][col] = 1

    if (solveNQUtil(board, col + 1))
        return true;

    board[i][col] = 0; // BACKTRACK
}

}

return false; }

bool solveNQ() { int board[N][N] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 } };

if (solveNQUtil(board, 0) == false) { printf("Solution does not exist"); return false; }

printSolution(board); return true; }

int main() { solveNQ(); return 0; }

swethareddy18 / Design-and-analysis-algorithm

N queens problem #25

define N 4

include

include