How do I implement backtracking in Python?

How do I implement backtracking in Python?

Backtracking is a problem-solving technique that involves exploring all possible solutions. In Python, you can implement it using recursion. Would you like an example?

Yes, please provide an example of backtracking in Python.

Sure! A classic example is solving the N-Queens problem. Here's a simple implementation:

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

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

print(solve_n_queens(4))

What does this code do?

This code attempts to place N queens on an N x N chessboard such that no two queens threaten each other. It uses backtracking to explore all possible placements.