swarooprath

class Solution {

    private static final String DOT = ".";
    private static final String Q = "Q";

    public static void main(String[] args) {
        var soln = new Solution().solveNQueens(8);
        for (var s : soln) {
            for (var r : s) {
                System.out.println(r);

swarooprath

class Solution:
    def solveNQueens(self, n: int) -> List[List[str]]:

        def solve_helper(n, slate, i):
            nonlocal result_list
            if i >= n:
                result_list.append(slate[:])
            else:
                for j in filter(lambda x: not is_attack(slate, x), range(n)):
                    slate.append(j)

swarooprath

class Solution:
    def solveNQueens(self, n: int) -> List[List[str]]:

        def solve_helper(n, slate, new_col):
            nonlocal result
            if new_col >= n:
                result.append(slate[:]) # copy the slate, else we will have empty lists in result as elements are removed from slate
            else:
                for new_row in filter(lambda nr: not is_attack(slate, nr, new_col), range(n)): # find the position where the new queen in the new column is not being attacked by existing queens on the board
                    slate.append(new_row)

swarooprath

class Tree(object):
    def __init__(self, val, children=[]):
        self.val = val;
        self.children = children;

    def __str__(self, level=0, depth=0):
        if depth == 0:
            depth = self.getDepth()
        ret = "\t" * level + repr(self.val) + ("____" * depth) + "\n"
        for child in self.children: