11526 - H(n)

[brianfry713]

For n=2147483647, the output should be 46475828386. Read this thread for ideas on a faster algorithm.

[RookiE3]

How to avoid time-limit exceed in this problem. All I know is the most obvious procedure will give time-limit exceed error. So where can I learn the faster algorithm from, pleeeeze anyone...

[brianfry713]

Read this thread for ideas on a faster algorithm.

[RookiE3]

Why is this code getting WA?

Code: Select all

#include <stdio.h>
#include <math.h>
int main()
{
   int n, T, sqrtn, i, l1, l2, k;
    unsigned long long sum, sum2;
    scanf("%d", &T);

    while(T--)
    {
        scanf("%d", &n);
        if(n < 0)
            n = -n;
        sum = n;
        sqrtn = sqrt(n);
        k = 1, l2 = n;
        for(i=2; i<=sqrtn; i++)
        {
            l1 = n/i;
            sum += l1;
            if(l2 != i)
                sum += k * (l2 - l1);
            l2 = l1;
            k++;
        }
        while(i <= l2)
        {
            sum += n / i;
            i++;
        }

        printf("%llu", sum);
        if(T)
            printf("\n");
    }
    return 0;
}

Anyone, please help!!!!

[lighted]

I sent you private message. Check it