Implement the N-Queens Problem - Implement the N-Queens Algorithm

Python
1

Tell us what’s happening:

What’s going on? I genuinely cannot find any difference in what the stories are asking for and what the function is returning

Your code so far

cols = set()
diag1 = set()
diag2 = set()
solutions = []

def dfs_n_queens(n):
    if n < 1:
        return []

    current = []   # store column for each row

    def is_safe(row, col):
        return (col not in cols and
                (row - col) not in diag1 and
                (row + col) not in diag2)

    def solve(row):
        if row == n:
            solutions.append(current.copy())
            return
        
        for col in range(n):
            if is_safe(row, col):
                # place
                cols.add(col)
                diag1.add(row - col)
                diag2.add(row + col)
                current.append(col)

                solve(row + 1)

                # undo
                cols.remove(col)
                diag1.remove(row - col)
                diag2.remove(row + col)
                current.pop()

    solve(0)
    return solutions

print(dfs_n_queens(5))

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Challenge Information:

Implement the N-Queens Problem - Implement the N-Queens Algorithm

2

Adding another function call at the bottom, might give some idea what’s happening:

print(dfs_n_queens(5))
print(dfs_n_queens(1))