What are some common backtracking techniques in Python?

What are some common backtracking techniques in Python?

Common backtracking techniques in Python include solving puzzles like Sudoku, N-Queens, and generating permutations.

Can you explain how backtracking works with 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. Backtracking is used to explore all possible placements.

What is the basic algorithm for backtracking?

The basic algorithm involves choosing a candidate, checking if it leads to a solution, and if not, backtracking to try the next candidate.

Can you provide a simple code example for backtracking in Python?

Absolutely! Here's a simple example for the N-Queens problem:

def solve_n_queens(n):
    def backtrack(row, columns, diagonals1, diagonals2):
        if row == n:
            return 1
        count = 0
        for col in range(n):
            if col in columns or (row - col) in diagonals1 or (row + col) in diagonals2:
                continue
            columns.add(col)
            diagonals1.add(row - col)
            diagonals2.add(row + col)
            count += backtrack(row + 1, columns, diagonals1, diagonals2)
            columns.remove(col)
            diagonals1.remove(row - col)
            diagonals2.remove(row + col)
        return count
    return backtrack(0, set(), set(), set())

This function counts the number of solutions for placing N queens.