eight queens problem in Python

Question

8-queens problem in Python.

Hi! I only start teaching Python, so could someone explain the code written below (found in the Internet)? Some pieces of the code are compli

Answer 1

Here is my solution. It is much more easier to understand and straighforward:

def under_attack(row, column, existing_queens):
    if not len(existing_queens): return False
    for queen in existing_queens:
        if not len(queen):
            continue
        r,c = queen
        if r == row: return True # Check row
        if c == column: return True # Check column
        if (column-c) == (row-r): return True # Check left diagonal
        if (column-c) == -(row-r): return True # Check right diagonal
    return False

def iter_solve(n):
    solutions = None
    for row in range(1, n+1):
        # for each row, check all valid column
        solutions = check(solutions, row, n)
    return solutions

def check(solutions, row, n):
    new_solutions = []
    for column in range(1, n+1):
        if not solutions or not len(solutions):
            new_solutions.append([] + [(row, column)])
        else:
            for solution in solutions:
                if not under_attack(row, column, solution):
                    new_solutions.append(solution + [(row, column)])
    return new_solutions