LeetCode52. N-Queens II

题目：

Follow up for N-Queens problem.

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

代码：

class Solution {public:    int count = 0;    int totalNQueens(int n) {        std::vector<int> v(n, 0);        vector<vector<int>> map(n, v);        queen(map, 0);        return count;    }    bool check(vector<vector<int>> map, int col, int row) {        for (int i = 0; i < row; i++) {            for (int j = 0; j < (int)map.size(); j++) {                if (map[i][j]) {                    if (abs(i - row) == abs(j - col)) {                        return false;                    }                    if (j == col)                        return false;                }            }        }        return true;    }    void queen(vector<vector<int>> map, int row) {        for (size_t i = 0; i < map.size(); i++) {            if (check(map, i, row)) {                //count++;                map[row][i] = 1;                if (row == (int)(map.size() - 1)) {                    map[row][i] = 0;                    count++;                    return;                }                queen(map, row+1);                map[row][i] = 0;            }        }    }};