HDU 6182A Math Problem（快速幂）

A Math Problem

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1632    Accepted Submission(s): 580

Problem Description

You are given a positive integer n, please count how many positive integers k satisfy kk≤n.

 

Input

There are no more than 50 test cases.

Each case only contains a positivse integer n in a line.

1≤n≤1018

 

Output

For each test case, output an integer indicates the number of positive integers k satisfy kk≤n in a line.

 

Sample Input

14

 

Sample Output

12

 

Source

2017ACM/ICPC广西邀请赛-重现赛（感谢广西大学）

想法：快速幂+暴力过

代码：

#include<stdio.h>#include<string.h>#include<math.h>typedef long long LL;LL pow(LL a,int b){    LL ans=1,base=a;    while (b>0)    {        if (b%2==1)            ans=base*ans;        base=base*base;        b/=2;    }    return ans;}int main(){    long long n;    while(scanf("%lld",&n)!=EOF)    {       long long i,k;       for(i=15;i>=1;i--)       {           if(pow(i,i)<=n)           {               k=i;               break;           }       }       printf("%lld\n",k);    }    return 0;}