Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions.
class Solution {
public:
int totalNQueens(int n) {
int check[n];
int sum=0;
calc(n,check,sum,0);
return sum;
}
void calc(int& n,int* check,int& sum,int step)
{
if(step==n)
{
sum++;
return;
}
for(int i=0;i<n;i++)
{
bool ok=true;
for(int j=0;j<step;j++)
if(check[j]==i || i-check[j]==step-j || check[j]-i==step-j)
{
ok=false;
break;
}
if(ok)
{
check[step]=i;
calc(n,check,sum,step+1);
}
}
}
};
public:
int totalNQueens(int n) {
int check[n];
int sum=0;
calc(n,check,sum,0);
return sum;
}
void calc(int& n,int* check,int& sum,int step)
{
if(step==n)
{
sum++;
return;
}
for(int i=0;i<n;i++)
{
bool ok=true;
for(int j=0;j<step;j++)
if(check[j]==i || i-check[j]==step-j || check[j]-i==step-j)
{
ok=false;
break;
}
if(ok)
{
check[step]=i;
calc(n,check,sum,step+1);
}
}
}
};