COJ 0024 N皇后问题

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<queue>
#include<cstring>
#define PAU putchar(' ')
#define ENT putchar('\n')
using namespace std;
const int maxn=25;
int ans=0,a[maxn],n;
bool check(int t){
for(int i=0;i<t;i++) if(a[t]==a[i]||t+a[t]==i+a[i]||t-a[t]==i-a[i]) return false;
return true;
}
void dfs(int d){
if(d==n){ans++;return;}
for(int i=0;i<n;i++){
a[d]=i;if(check(d)) dfs(d+1);
} return;
}
inline int read(){
int x=0,sig=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')sig=-1;ch=getchar();}
while(isdigit(ch))x=10*x+ch-'0',ch=getchar();
return x*=sig;
}
inline void write(int x){
if(x==0){putchar('0');return;}if(x<0)putchar('-'),x=-x;
int len=0,buf[15];while(x)buf[len++]=x%10,x/=10;
for(int i=len-1;i>=0;i--)putchar(buf[i]+'0');return;
}
void init(){
n=read();
dfs(0);write(ans);
return;
}
void work(){
return;
}
void print(){
return;
}
int main(){init();work();print();return 0;}