CODEWITHSUNDEEP
c++performance
Lakshay Chhikara
Lakshay Chhikara

Reputation: 186

Reducing time in the following code

I gave this solution at the codechef for the problem code : FCTRL.

I saw the compile time of others people using the same the language c ( i am using c++ gcc 4.8.1) is somewhat less, mine is 0.46s while their is 0.23

Can somebody help me in reducing the time if possible?

#include<iostream>
using namespace std;
int main()
{
    long int t,i,temp;
    cin>>t;
    long int n[t],a[t];
    for(i=0;i<t;i++)
    {
        temp=1;
        a[i]=0;
        cin>>n[i];
        while(temp)
        {
            temp=n[i]/5;
            a[i]+=temp;
            n[i]=n[i]/5;
        }
    }
    for(i=0;i<t;i++)
    cout<<a[i]<<"\n";

    return(0);
}

Upvotes: 1

Views: 126

Answers (2)

Matthieu M.
Matthieu M.

Reputation: 299730

You worst offense to C++ is using Variadic-Length arrays, those are non-standards.

And in fact, it turns out you absolutely do not need them. This problem can be solved on a line-per-line basis so using arrays to hold the input and output is useless.

Here is your program, simplified. I also noted that temp was useless within the loop (though it was likely optimized out anyway, it polluted the code).

#include <iostream>

int main()
{
    size_t number = 0;
    std::cin >> number;

    for(size_t i = 0 ; i < number; ++i)
    {
        size_t a = 0, n = 0;

        std::cin >> n;

        while (n)
        {
            n /= 5;
            a += n;
        }

        std::cout << a << '\n';
    }
}

Is it possible to do better ? Oh yes! The main issues here is that the C++ streams are none too fast so you may get a good boost by switching to the C reading methods... however they are not as nice (and safe).

Upvotes: 0

Saksham
Saksham

Reputation: 9380

From your description, as you are using c++ and they are using c, it might be due to how the compiler handles each instruction.

Also you may try replacing

temp=n[i]/5;
a[i]+=temp;
n[i]=n[i]/5;

By

temp=n[i]/5;
a[i]+=temp;
n[i]=temp;    //why compute the value again

And see if some time reduces or not

Upvotes: 1

Related Questions