leetcode.52. N-Queens II

Follow up for N-Queens problem.

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


class Solution {
public:
int count = 0;
int totalNQueens(int n) {
vector<int> vi(n);
solveNQueens(vi, n, 0);
return count;
}
void solveNQueens(vector<int> &vi, int n, int c)
{
if(c == n)
{
count++;
return;
}
for(vi[c] = 0; vi[c] < n; ++ vi[c])
if(safe(vi, n, c))
solveNQueens(vi, n, c + 1);
}

bool safe(vector<int> &vi, int n, int c)
{
for(int i = 0; i < c; ++ i)
if(vi[i] == vi[c] || abs(vi[c] - vi[i]) == abs(c - i))
return false;
return true;
}

};