وزیر n

main.cpp

#include<bits/stdc++.h>
using namespace std;


long long ans;
const int MAX_N = 8;
bool row[MAX_N];
bool diag1[MAX_N*2];
bool diag2[MAX_N*2];

void kQueen(int n, int k, int col){
    if(col == n){ /// exit condition
        if( k == 0) ans ++;
        return ;
    }
    for(int i = 0; i < n; i++){
        if(row[i]) continue; /// there is a queen in this row
        if(diag1[ i + col ]) continue; /// there is a queen(a,b) that i + col = a +b
        if(diag2[ i - col + MAX_N ] ) continue;/// 0 <= i-col+MAX_N < 2*MAX_N : there is a queen(a,b) that i - col = a -b
        row[i] = diag1[ i+col ] = diag2[ i-col + MAX_N ] = true; /// change grid : put a queen in (col, i)
        kQueen(n, k-1, col+1);
        row[i] = diag1[ i+col ] = diag2[ i-col + MAX_N ] = false; /// undo last change
    }
    kQueen(n, k, col+1); /// don't put any queen on this column

}

int main(){
    int n,k;
    cin >> n >> k;
    kQueen(n, k, 0);
    cout << ans << endl;
}