LeetCode N-Queens II

题目：

Follow up for N-Queens problem.

Now, instead outputting board configurations, return the total number of distinct solutions.

class Solution {public:int totalNQueens(int n) {res = 0;memset(used, false, sizeof(used));dfs(0, n);return res;}private:int res;// a[i]表示第i行的a[i]列有Queenint a[100];int used[100];void dfs(int dep, int maxDep) {if (dep == maxDep) {res++;return;}for (int y = 0; y < maxDep; y++) {if (check(dep, y) && !used[y]) {used[y] = true;a[dep] = y;dfs(dep + 1, maxDep);used[y] = false;}}}bool check(int x, int y) {for (int i = 0; i < x; i++) {if (abs(i-x) == abs(y-a[i]))return false;}return true;}};