N-Queens II

Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions.



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 Backtracking

ddd

class Solution {
public:

bool isValidQueens(vector<int> &A,int r)
{
for(int i=0;i<r;i++)
{
if((A[i]==A[r])||(abs(A[i]-A[r]))==(r-i))
return false;
}
return true;
}

void nQueens(int cur,int n,int &result,vector<int> &A)
{
if(cur == n)
{
result++;
return;
}
else
{
for(int i = 0;i<n;i++)
{
A[cur] = i;
if(isValidQueens(A,cur))
nQueens(cur + 1,n,result,A);
A[cur] = -1;
}
}
}

int totalNQueens(int n) {
int result = 0;
vector<int> A(n,-1);
nQueens(0,n,result,A);
return result;

}
};