leetcode: 52. N-Queens II

# Follow up for N-Queens problem.
# 
# Now, instead outputting board configurations, return the total number of distinct solutions.

class Solution():
    def totalNQueens(self, n):
        from functools import reduce
        def solveNQueensRecu(solution, row, n):
            if row == n:
                solutions.append(list(map(lambda x: '.' * x + "Q" + '.' * (n - x - 1), solution)))
            else:
                for i in range(n):
                    if i not in solution and reduce(lambda acc, j: abs(row - j) != abs(i - solution[j]) and acc, range(len(solution)), True):
                        solveNQueensRecu(solution + [i], row + 1, n)
        solutions = []
        solveNQueensRecu([], 0, n)
        return len(solutions)


if __name__ == "__main__":
    assert Solution().totalNQueens(8) == 92