HDU 5578 abs (BestCoder Round #85 C)素数筛+暴力

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <map>
#include <queue>
#include <vector>
using namespace std;
typedef  long long LL;
const int N = 1e5+5;
bool v[N];
int prime[N>>1],cnt;
void getprime(){
  for(int i=2;i*i<=N-5;++i)
    if(!v[i])
      for(int j=i*i;j<=N-5;j+=i)
        v[j]=1;
  for(int i=2;i<=N-5;++i)
  if(!v[i])prime[++cnt]=i;
}
LL fun(LL x,LL y){
  if(x>y)swap(x,y);
  return y-x;
}
int main(){
  int T;
  getprime();
  scanf("%d",&T);
  while(T--){
    LL n;scanf("%I64d",&n);
    LL x=(LL)(sqrt(1.0*n)+0.5),l=-1,r=-1;
    for(int k=x;k>=2;--k){
     bool flag=false;
     for(int i=1;i<=cnt&&1ll*prime[i]*prime[i]<=k;++i){
      if(k%(1ll*prime[i]*prime[i])==0){flag=true;break;}
     }
     if(!flag){l=k;break;}
    }
    for(int k=x+1;;++k){
       bool flag=false;
     for(int i=1;i<=cnt&&1ll*prime[i]*prime[i]<=k;++i){
      if(k%(1ll*prime[i]*prime[i])==0){flag=true;break;}
      
    }if(!flag){r=k;break;}
   }
   LL ret;
   if(l==-1)ret=fun(r*r,n);
   else ret=min(fun(n,l*l),fun(r*r,n));
    printf("%I64d\n",ret);
  }
  return 0;
}