HDU5778之暴力枚举

abs

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 391 Accepted Submission(s): 137

Problem Description
Given a number x, ask positive integer y≥2, that satisfy the following conditions:
1. The absolute value of y - x is minimal
2. To prime factors decomposition of Y, every element factor appears two times exactly.

Input
The first line of input is an integer T ( 1≤T≤50)
For each test case，the single line contains, an integer x ( 1≤x≤1018)

Output
For each testcase print the absolute value of y - x

Sample Input
5
1112
4290
8716
9957
9095

Sample Output
23
65
67
244
70

代码：

#include 
#include 
#include 
#include 
#include 
const long long INF = 0x7fffffffffffffffll;
using namespace std;
long long ans;
long long n;
bool work(long long x)
{
    if(x<2)
        return false;
    long long t=x;
    for(long long i=2;i*i<=x;i++)
    {
        if(x%i==0)
        {
            if(x%(i*i)==0)//出现了超过一次
            {
                return false;
            }
            x/=i;
        }
    }
    ans=min(ans,abs(t*t-n));
    return true;
}
int main (void)
{
    int t;
    cin>>t;
    while(t--)
    {
        scanf("%I64d",&n);
        long long x=(long long)(sqrt(n)+0.5);
        int flag=0;
        ans=INF;
        for(int i=0;;i++)
        {
            if(work(x+i))
                flag=1;
            if(work(x-i))
                flag=1;
            if(flag==1)
                break;
        }
        printf("%I64d\n",ans);
    }
    return 0;
}