(数论)LightOJ -- 1245
http://acm.hust.edu.cn/vjudge/contest/view.action?cid=98634#problem/B(acm14)
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
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <map> using namespace std; #define N 200005 int main()
{
long long T, iCase=; scanf("%d", &T); while(T--)
{
long long n, i; scanf("%lld", &n); long long a, num = , sum = n, pre=n; for(i=; i<=n; i++)
{
a = n/i;
num += (pre-a);
sum += (pre-a)*(i-); if(num==n)
break; num++;
sum += a;
if(num==n)
break; pre = a;
} printf("Case %lld: %lld\n", iCase++, sum);
} return ;
}
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