Implement N-Queen Problem

#include <stdio.h>
#include <stdbool.h>
#define N 8

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) {
    if (col >= N)
        return true;

    for (int i = 0; i < N; i++) {
        if (isSafe(board, i, col)) {
            board[i][col] = 1;
            if (solveNQUtil(board, col + 1))
                return true;
            board[i][col] = 0;
        }
    }

    return false;
}

bool solveNQ() {
    int board[N][N];
    for (int i = 0; i < N; i++)
        for (int j = 0; j < N; j++)
            board[i][j] = 0;

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

    printSolution(board);
    return true;
}

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

Explanation:

• The program uses the backtracking technique to solve the N-Queens problem, where N queens are to be placed on an NxN chessboard in such a way that no two queens threaten each other.
• printSolution() function prints the solution of the N-Queens problem.
• isSafe() function checks if it's safe to place a queen at a given position on the chessboard.
• solveNQUtil() is a recursive utility function that tries placing queens one by one in different columns.
• solveNQ() initializes the chessboard and starts the solving process.
• In main(), the solveNQ() function is called to solve the N-Queens problem for a chessboard of size 8x8 (N=8).