leetcode-cpp/0052-n-queens-ii.cpp at main · j414j/leetcode-cpp · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
#include<string>
#include<vector>
using namespace std;

class Solution {
public:
    int _n, ans;
    vector<vector<bool>> curr;
    vector<bool> col;
    int dirs[4][2] = {{-1, -1}, {-1, 1}};
    void recur(int row) {
        for (int i = 0; i < _n; i++) {
            if (col[i])
                continue;
            bool isSafe = true;
            for (int j = 1; j < _n; j++) {
                for (auto dir : dirs) {
                    int nrow = row + j * dir[0];
                    int ncol = i + j * dir[1];
                    if (nrow < 0 || ncol < 0 || nrow >= _n || ncol >= _n)
                        continue;
                    if (curr[nrow][ncol]) {
                        isSafe = false;
                        break;
                    }
                }
                if (!isSafe)
                    break;
            }
            if (isSafe) {
                curr[row][i] = true;
                col[i] = true;
                if (row == _n - 1)
                    ans++;
                else
                    recur(row + 1);
                curr[row][i] = false;
                col[i] = false;
            }
        }
    }
    int totalNQueens(int n) {
        _n = n;
        ans = 0;
        curr.resize(n, vector<bool>(n, false));
        col.resize(n, false);
        recur(0);
        return ans;
    }
};