class Solution(object):    def __init__(self):        self.queenList = []        self.result = []        self.charList = []        def solveNQueens(self, n):        for i in range(0,n):            self.charList.append(".")        self.currLayer(0,n)        return self.result                        """        :type n: int        :rtype: List[List[str]]        """    def currLayer(self, x, n):        if(x==n):            result = []            for queen in self.queenList:                self.charList[queen[1]] = "Q"                result.append("".join(self.charList))                self.charList[queen[1]] = "."                      self.result.append(result)            return        for y in range(0,n):            temp = (x,y)            if(self.ableToPutDown(temp)):                self.queenList.append(temp)                self.currLayer(x+1,n)                self.queenList.pop()    def ableToPutDown(self, temp):        for queen in self.queenList:            if( queen[1] == temp[1] ):#same col                return False            elif( abs(queen[0]-temp[0]) == abs(queen[1]-temp[1]) ):#same diagonal                return False        return True