hdu 2011

打表做的，需要注意的是打表时，没有用下标0，从1开始

#include<bits/stdc++.h>

using namespace std;
int main()
{
    float a[1002]={0,1},sum[1002]={0,1};
    for(int i = 2; i < 1001;i++){
        a[i] = 1.0 / i;
        if(i%2==0)
            a[i] = (-1)*a[i];
        //cout << a[i] << endl;
        sum[i] = sum[i-1] + a[i];
    }
    int n;
    scanf("%d",&n);
    while(n--){
        int t;
        scanf("%d",&t);
        printf("%.2f
",sum[t]);
    }
    return 0;
}