How do I solve the N-Queens problem?

What is the N-Queens problem?

The N-Queens problem is a classic algorithmic problem where you need to place N queens on an N×N chessboard so that no two queens threaten each other.

How can I approach solving it?

You can use backtracking, a recursive algorithm that tries to place queens one by one in different columns and checks for conflicts.

Can you show me a simple code example?

Sure! Here's a Python example using backtracking:

def solve_n_queens(n):
    def is_safe(board, row, col):
        for i in range(col):
            if board[row][i] == 1:
                return False
        for i, j in zip(range(row, -1, -1), range(col, -1, -1)):
            if board[i][j] == 1:
                return False
        for i, j in zip(range(row, n, 1), range(col, -1, -1)):
            if board[i][j] == 1:
                return False
        return True

    def solve_util(board, col):
        if col >= n:
            return True
        for i in range(n):
            if is_safe(board, i, col):
                board[i][col] = 1
                if solve_util(board, col + 1):
                    return True
                board[i][col] = 0
        return False

    board = [[0] * n for _ in range(n)]
    if not solve_util(board, 0):
        return "No solution exists"
    return board

This code defines a function to solve the N-Queens problem.