LeetCode N-Queens

The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other.

Given an integer n, return all distinct solutions to the n-queens puzzle.

Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space respectively.

For example,
There exist two distinct solutions to the 4-queens puzzle:

[ [".Q..",  // Solution 1  "...Q",  "Q...",  "..Q."], ["..Q.",  // Solution 2  "Q...",  "...Q",  ".Q.."]]

class Solution {public:vector<vector<string> > solveNQueens(int n) {vector<vector<string> > Array;vector<int> ivec;//初始化数组，使得 ivec[i] = ifor (int i = 0; i < n; ++i) {ivec.push_back(i);}func(Array, ivec, 0, n);return Array;}void func(vector<vector<string> > &Array, vector<int> &ivec, int start, int last) {//判断是否到结尾，是就说明是全排列中的一种if (start == last) {//判断是否满足 皇后之间不能吃，斜对角线和反斜对角线for (int i = 0; i < last; ++i) {for (int j = i + 1; j < last; ++j) {if (i - j == ivec[i] - ivec[j] || j - i == ivec[i] - ivec[j])return;}}//保存皇后位置vector<string> tempvec;for (int i = 0; i < last; ++i) {string str;for (int j = 0; j < ivec[i]; ++j) {str += ".";}str += "Q";for (int j = ivec[i] + 1; j < last; ++j) {str += ".";}tempvec.push_back(str);}Array.push_back(tempvec);return;}//循环加递归 做全排列for (int i = start; i < last; ++i) {swap(ivec[i], ivec[start]);func(Array, ivec, start + 1, last);swap(ivec[i], ivec[start]);}}};