Follow up for N-Queens problem.
Now, instead outputting board configurations, return the total number of distinct solutions.
#include<iostream>
#include
<vector>
#include
<cmath>
using
namespace
std;
class
Solution
{
public
:
int
res=
0
;
int
totalNQueens(
int
n)
{
vector
<
int
> state(n,-
1
);
helper(n,
0
,state);
return
res;
}
void
helper(
int
n,
int
start,vector<
int
> &
state)
{
if
(start==
n)
{
res
++
;
return
;
}
int
i;
for
(i=
0
; i<n; i++
)
{
if
(isValid(state,start,i))
{
state[start]
=
i;
helper(n,start
+
1
,state);
state[start]
=-
1
;
}
}
}
bool
isValid(vector<
int
> &state,
int
row,
int
col)
{
int
i;
for
(i=
0
; i<row; i++
)
if
(state[i]==col||row-i==abs(state[i]-
col))
return
false
;
return
true
;
}
};
int
main()
{
Solution s;
cout
<<s.totalNQueens(
4
)<<
endl;
}
