B - 四月纲领 light oj 1245【数论】

B - 四月纲领

Time Limit:3000MS     Memory Limit:32768KB     64bit IO Format:%lld & %llu

Submit Status Practice LightOJ 1245

Description

I was trying to solve problem '1234 - Harmonic Number', I wrote the following code

long long H( int n ) {
    long long res = 0;
    for( int i = 1; i <= n; i++ )
        res = res + n / i;
    return res;
}

Yes, my error was that I was using the integer divisions only. However, you are given n, you have to find H(n) as in my code.

Input

Input starts with an integer T (≤ 1000), denoting the number of test cases.

Each case starts with a line containing an integer n (1 ≤ n < 2³¹).

Output

For each case, print the case number and H(n) calculated by the code.

Sample Input

11

1

2

3

4

5

6

7

8

9

10

2147483647

Sample Output

Case 1: 1

Case 2: 3

Case 3: 5

Case 4: 8

Case 5: 10

Case 6: 14

Case 7: 16

Case 8: 20

Case 9: 23

Case 10: 27

Case 11: 46475828386

代码：

#include<cstdio>#include<cmath>typedef long long ll;int main(){int t;int n;int cnt=0;scanf("%d",&t);while(t--){ll sum=0;scanf("%d",&n);int i;for(i=1;i<=(int)sqrt(n);i++){sum+=n/i;if(n/i>n/(i+1))sum+=(ll)((n/i-n/(i+1))*i);}i--;if(n/i==i)sum-=i;printf("Case %d: %lld\n",++cnt,sum);}return 0;}