hdu5778 abs

http://acm.hdu.edu.cn/showproblem.php?pid=5778

出现两次这种特殊的直接就是开方，但是规模依然过大，所以这个时候从x向两边暴力枚举

根据素数定理，logn就能碰到一个质数，所以时间复杂度合适

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<algorithm>
#include<functional>
#include<iostream>
#include<cmath>
#include<string>
#include<cctype>
#include<stack>
#include<queue>
#include<set>
#include<sstream>
#include<map>
using namespace std;
#define For(i,k,n) for(int i=k;i<=n;i++)
#define ForD(i,k,n) for(int i=n;i>=k;i--)
#define Lson (u<<1)
#define Rson ((u<<1)+1)
#define MEM(a) memset(a,0,sizeof(a));
#define NEG(a) memset(a,-1,sizeof(a));
#define FILL(a) memset(a,0x3f,sizeof(a));
#define INF 0x3f3f3f3f
#define LLINF 0x3f3f3f3f3f3f3f3f
#define ll long long
#define printbin(b,a){int tmp=a;string s;do{s+=tmp%2+'0';tmp/=2;}while(tmp);reverse(s.begin(),s.end());cout<<"bin "<<b<<"="<<s<<endl;}
#define printarr(i,a,f,b) {For(i,f,b) cout<<a[i]<<" "; printf("\n");}
#define ptf printf("fuck\n")
#define pt(a) cout<<a<<endl
#define flgprint(flg,a,b) {if(flg) printf("%s\n",a);else printf("%s\n",b);}
#define fp   freopen("in.txt","r",stdin)

int check(ll x)
{
    ll lim=(ll)sqrt(x)+1;
    For(i,2,min(lim,x))
    {
        if(x%i==0)
        {
            x/=i;
            if(x%i==0) return 0;
        }
    }
    return 1;
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {

        ll x,ans=LLINF;
        scanf("%lld",&x);
        if(x<=4) ans=4-x;
        else{
        long long t=sqrt(x),m,l;
        for(l=0;; l++)
        {
            m=t+l;
            if(m*m>=x&&check(m))
                {
                    ans=abs(m*m-x);
                    break;
                }
        }
        long long k=x-ans;
        for(long long i=0;;i++)
        {
            m=t-i;
            if(m*m<=k) break;
            if(check(m)) ans=min(ans,abs(m*m-x));
        }
    }
        printf("%lld\n",ans);
    }
    return 0;
}