/
N-Queens_II.cpp
37 lines (34 loc) · 1018 Bytes
/
N-Queens_II.cpp
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
// Follow up for N-Queens problem.
// Now, instead outputting board configurations,
// return the total number of distinct solutions.
class Solution {
public:
bool check(vector<int> &queenPos, int row, int col, int n) {
for (int i = 0; i < row; i++) {
if (queenPos[i] == col)
return false;
if (abs(i-row) == abs(queenPos[i]-col))
return false;
}
return true;
}
void putQueen(vector<int> &queenPos, int row, int n, int &result) {
if (row == n) {
result++;
return;
}
for (int col = 0; col < n; col++) {
if (check(queenPos, row, col, n)) {
queenPos[row] = col;
putQueen(queenPos, row+1, n, result);
queenPos[row] = -1;
}
}
}
int totalNQueens(int n) {
int result = 0;
vector<int> queenPos(n, -1);
putQueen(queenPos, 0, n, result);
return result;
}
};