What are some examples of backtracking in Python?

What are some examples of backtracking in Python?

Backtracking is a problem-solving technique that involves exploring all possible solutions and abandoning those that fail to satisfy the constraints. A classic example in Python is solving the N-Queens problem.

Can you explain the N-Queens problem?

Sure! The N-Queens problem involves placing N queens on an N×N chessboard so that no two queens threaten each other. This means no two queens can be in the same row, column, or diagonal.

How would you implement this in Python?

You can implement it using a recursive function that places queens one row at a time and backtracks when a conflict is detected. Would you like to see the code?

Yes, please share the code!

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), 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 []
    return board

This code sets up the board and uses backtracking to find a solution.