8 Queens Problem in Python: Code & Explanation

This page demonstrates how to solve the 8 queens problem in Python. You'll find clear code examples, explanations, and tips for understanding and implementing the solution.

Python Code Example

def solve_nqueens(n):
    solutions = []
    board = []
    def is_safe(row, col):
        for r, c in enumerate(board):
            if c == col or abs(row - r) == abs(col - c):
                return False
        return True
    def backtrack(row=0):
        if row == n:
            solutions.append(list(board))
            return
        for col in range(n):
            if is_safe(row, col):
                board.append(col)
                backtrack(row + 1)
                board.pop()
    backtrack()
    return solutions

print(solve_nqueens(8))

How the Code Works

The function solve_nqueens uses recursion and backtracking to explore all possible placements of queens. The is_safe function checks for conflicts, and the backtrack function tries each column in the current row. When a valid arrangement is found, it is added to the list of solutions.

Tips for Understanding

• Print the board at each step to visualize the process.
• Try changing the board size to solve the N-Queens problem for different N.
• Experiment with optimizations, such as using sets to track columns and diagonals.

FAQ