Harmonic Number LightOJ - 1234 （分段打表）

#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define maxn 100000000
#define Pair pair<int, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int LL_INF = 0x7fffffffffffffff,INF = 0x3f3f3f3f;
double ch[maxn/50+10];
int main()
{
    int T, cnt = 1;
    double sum = 0;
    ch[0] = 0;
    for(int i=1; i<=maxn; i++)
    {
        sum += 1/(double)i;
        if(i % 50 == 0)
            ch[cnt++] = sum;
    }
    int kase = 0;
    cin>> T;
    while(T--)
    {
        int n;
        cin>> n;
        double m = ch[n/50];
        for(int i=n/50*50+1; i<=n; i++)
            m += 1/(double)i;
        printf("Case %d: %.10f\n",++kase,m);    

    }
    

    return 0;
}