[leetcode] 52. N-Queens II

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Follow up for N-Queens problem.

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

这道题和第51题基本没有太大区别，题目难度为Hard。

如果需要详细解释请看第51题（传送门），具体代码：

class Solution {public:    int totalNQueens(int n) {        vector<string> curRst(n, string(n, '.'));        int cnt = 0;                NQueens(curRst, 0, n, cnt);                return cnt;    }        void NQueens(vector<string> &curRst, int row, int n, int &cnt) {        if(row == n) {            cnt++;            return;        }                for(int i=0; i<n; i++) {            bool flag = true;            for(int j=0; j<row; j++) {                if(curRst[j][i] == 'Q') {                    flag = false;                    break;                }                if((i+j-row >= 0) && (i+j-row <= n-1) && (curRst[j][i+j-row] == 'Q')) {                    flag = false;                    break;                }                if((i+row-j >= 0) && (i+row-j <= n-1) && (curRst[j][i+row-j] == 'Q')) {                    flag = false;                    break;                }            }                        if(flag) {                curRst[row++][i] = 'Q';                NQueens(curRst, row, n, cnt);                curRst[--row][i] = '.';            }        }    }};

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