Optimization of C++ code

Question

This is my solution to Spoj 11373. Coke madness

#include <cstdio>

int main(){
    int T; scanf("%d",&T);

    for(int j = 1; j <= T; j++){
        int n;
        scanf("%d",&n);
        long long sum = 0, small = 0;
        int t;
        for(int i = 0; i < n; i++) {
            scanf("%d",&t);
            sum += t;
            if( sum < small) small = sum;
        }
        printf("Scenario #%d: %lld\n", j, -1*small+1);
    }
}

The problem is simple. This solution takes 0.12 seconds on Spoj, though there are 0.01 second solutions. I am curious what optimizations may be done to this code to get faster. I thought -1*small+1 may be got using bit-wise operations but didn't find how. Also I can't get rid of long long since sum may exceed int.

This program is probably I/O bound, so I'm not sure you can make it faster (by improving CPU time only) — Basile Starynkevitch
– Basile Starynkevitch, Commented Feb 2, 2013 at 15:25
@David your suggestions didn't help so much, trying to read the input file at once — Ashot
– Ashot, Commented Feb 2, 2013 at 15:34
@David Riddle me this: do you know the difference between an int outside of a loop and one inside of it? — Yakk - Adam Nevraumont
– Yakk - Adam Nevraumont, Commented Feb 2, 2013 at 15:51

Puppy · Accepted Answer · 2013-02-02 15:26:01Z

11

You're making way too many I/O calls. Read the whole file at once, and then parse it, then create your output, and then write it all at once.

answered Feb 2, 2013 at 15:26

Puppy

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