description:
八皇后
Note:
Example:
Input: 4
Output: 2
Explanation: There are two distinct solutions to the 4-queens puzzle as shown below.
[
[".Q..", // Solution 1
"...Q",
"Q...",
"..Q."],
["..Q.", // Solution 2
"Q...",
"...Q",
".Q.."]
]
answer:
class Solution {
public:
int totalNQueens(int n) {
int res = 0;
vector<int> pos(n, -1);
helper(pos, 0, res);
return res;
}
void helper(vector<int>& pos, int row, int& res) {
int n = pos.size();
if (row == n) ++res;
for (int col = 0; col < n; ++col) {
if (isValid(pos, row, col)) {
pos[row] = col;
helper(pos, row + 1, res);
pos[row] = -1;
}
}
}
bool isValid(vector<int>& pos, int row, int col) {
for (int i = 0; i < row; ++i) {
if (col == pos[i] || abs(row - i) == abs(col - pos[i])) {
return false;
}
}
return true;
}
};
relative point get√:
hint :
和上面那个题一样