二分的思想

#include<iostream>
#include<cmath>
using namespace std;
long long n;
long long rightt,leftt,middle;
int main(){
	scanf("%lld",&n);
	rightt=sqrt(n);
	while(leftt<rightt){
		
		middle=(rightt+leftt)/2;
		if((middle*middle*middle<=n)&&(pow(middle+1,3)>n)){
			leftt=middle;
			break;
		}
		else if(middle*middle*middle>n){
			rightt=middle-1;
		}
		else{
			leftt=middle+1;
		}
//		printf("%d %d\n",leftt,rightt); 
	}
			printf("%lld",leftt);
	return 0;
}