hdu 6216-A Cubic number and A Cubic Number 数学

Problem Description
A cubic number is the result of using a whole number in a multiplication three times. For example,  so  is a cubic number. The first few cubic numbers are  and . Given an prime number . Check that if  is a difference of two cubic numbers.
 

Input
The first of input contains an integer  which is the total number of test cases.
For each test case, a line contains a prime number .
 

Output
For each test case, output 'YES' if given  is a difference of two cubic numbers, or 'NO' if not.
 

Sample Input
10 2 3 5 7 11 13 17 19 23 29
 

Sample Output
NO NO NO YES NO NO NO YES NO NO
 

Source
输入输出测试

题意：给出一个质数，判断该质数是否为两立方数之差

分析：

一开始想暴力打表的，发现超内存了。

p=x^3-y^3=(x-y)*(x^2+x*y+y^2)为一个质数，则x-y=1

知道这一步就ok了，打表或者推公式
则p=3*y（y+1）+1

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;

typedef long long ll;
const int N=100010; 
int main(){
    int t;
    ll n;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lld",&n);
        if((n-1)%3==0)
        {
            n=(n-1)/3;
            ll j = sqrt(n);
            if(j*(j+1) == n)
                printf("YES\n");
            else
                printf("NO\n");
        }
        else 
          printf("NO\n");
    }
    return 0;
}