LightOJ 1245 - Harmonic Number (II) （找规律）

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LightOJ 1245 - Harmonic Number (II) （找规律）

angel_imp 2016-03-20 11:46:00 浏览3604

1245 - Harmonic Number (II)
 Time Limit: 3 second(s) Memory Limit: 32 MB

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.

Output for Sample Input

11

1

2

3

4

5

6

7

8

9

10

2147483647

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

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

…………

```#include <iostream>
#include <cmath>
using namespace std;
typedef long long LL;
int main()
{
int T;
LL n;
cin>>T;
for(int cas=1; cas<=T; cas++)
{
cin>>n;
int m = sqrt(n);
LL ret = 0;
for(int i=1; i<=m; i++)
ret += n/i;
for(int i=1; i<=m; i++)
ret += (n/i - n/(i+1))*i;
if(m == n/m)
ret -= m;
cout<<"Case "<<cas<<": "<<ret<<endl;
}
return 0;
}
```

angel_imp
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