【HDU - 6182】【A Math Problem 】

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 1 4   Sample Output 1 2   Source 2017ACM/ICPC广西邀请赛-重现赛（感谢广西大学） 解题思路：思考后会发现15^15就已经会爆long long 了，所以直接暴力求解1-15中符合条件的就欧克 ac代码： #include<algorithm> #include<iostream> #include<cstdio> #include<cstring> using namespace std; typedef long long ll; ll n; int k; ll ksm(ll a,ll b) { ll res=1; while(b) { if(b&1) res=res*a; a=a*a; b>>=1; } return res; } int main() { while(scanf("%lld",&n)!=EOF) { int ans=0; for(ll i=1;i<=15;i++) { if(ksm(i,i)>n) break; ans++; } printf("%d\n",ans); } return 0; }