【POJ1003】Hangover（二分搜索）

直接用库函数二分即可。

 #include <iostream>
 #include <cstring>
 #include <cstdlib>
 #include <cstdio>
 #include <cmath>
 #include <cctype>
 #include <algorithm>
 #include <numeric>
 
 #define eps 1e-8
 using namespace std;
 
 double len[];
 
 int main () {
     ios :: sync_with_stdio(false);
     len[] = ;
     for (int i = ; i < ; ++ i) {
         len[i] = len[i - ] + 1.0 / (double)(i + );
     }
 
     //cout << len[273] << endl;
     double n;
     while (cin >> n) {
         if (n -  < eps) {
             break;
         }
         //cout << lower_bound(len, len + 300, n) - &len[0] << endl;
         printf ("%d card(s)\n", lower_bound(len, len + , n) - &len[]);
     }
     return ;
 }