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 < 2).

Output

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

Sample Input

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

题意:就是计算所给的函数的值,但是咱们如果按函数那种算法会TLE,so

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath> using namespace std; int main()
{
int t, n, l = 1;
scanf("%d", &t);
while(t--)
{
scanf("%d", &n);
long long k = sqrt(n);
long long res = 0;
for(int i = 1; i < k+1; i++)
{
res += n /i;
if(n/i > n / (i+1))
res += (n/i - n / (i+1))*i;
if((k*k + i - 1) == n) // 在k*k到k*k+k-1中的数多加了k,so减去
{
res -= k;
}
}
printf("Case %d: %lld\n", l++, res);
}
return 0;
}

  

05-11 13:14
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