Optimization in sum of array in java

Question

I have an array and a long type variable called total that stands for it's sum.

If the array is of length n then the summation of it should be done like this: sum = arr[0] + arr[n-1] + arr[1] + arr[n-2] +... until sum >= total and I have to print a string of the elements in the sum

My Approach : I have executed loop till n/2 if n is even or n/2 + 1 if n is odd.

I am doing something like this :

String s = "";
if (n % 2 ==0)
     loop = n/2;
else 
     loop = n/2 + 1;

for(int i=0 ; i < loop ; i++){
     sum += arr[i];
     s += arr[i] + " ";
     if(check(sum , total)==true) break; //this function checks if sum>=total.
     sum += arr[n];
     s += arr[n] + " ";
     if(check(sum , total)==true) break;
     n--;
}
System.out.println(s);

Example : arr[ ]={10 , 20 , 30, 40, 50} and total = 120 then output should be :

10 50 20 40

my approach stills gives TLE in some test cases. I need more optimized solution than this. Help me here.

what's TLE? And how is check breaking the looping? Is it throwing an exception? — Eran
– Eran, Commented Sep 22, 2016 at 7:46
TLE is time limit exceeded and it is not throwing an exception. — Yash Mehta
– Yash Mehta, Commented Sep 22, 2016 at 7:48
There is no real reason to keep the string and concatenating it. Print as soon as you add. — RealSkeptic
– RealSkeptic, Commented Sep 22, 2016 at 7:51

xenteros · Accepted Answer · 2016-09-22 07:51:27Z

3

Why not to do that this way:

for (int i = 0; sum < total && i < loop; i++) {
    sum += array[i];
    System.out.print(String.valueOf(array[i]) + " ");
    if (sum < total) {
        sum+=array[n-1-i];
        System.out.print(String.valueOf(array[n-1-i]) + " ");
    }
}

answered Sep 22, 2016 at 7:51

xenteros

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4 Comments

Bathsheba Over a year ago

Upvoted. Out of interest, do the online judges penalise i++ over ++i?

xenteros Over a year ago

@Bathsheba why should they in Java on integers?

ChiefTwoPencils Over a year ago

@Bathsheba, that would be extremism for sure.

Bathsheba Over a year ago

These days I agree but are not these online judges a law unto themselves?

CodeKick · Accepted Answer · 2016-09-22 08:13:29Z

you can organise your array first the do the tratement. something like this :

String s = "";
orgArray(arr);

for(int i=0 ; i < (arr.lenght)-1; i++){
     sum += arr[i];
     s += arr[i] + " ";
     check(sum , total);
}
System.out.println(s);

and the function will be some thing like this :

public static void orgArray(string tab[]) {
        int longueur = tab.length;
        int tampon = 0;
        boolean permut;

        do {

            permut = false;
            for (int i = 0; i < longueur - 1; i++) {

                if (i + 1 < longueur - 1 - i) {

                    tampon = tab[i + 1];
                    tab[i + 1] = tab[longueur - 1];
                    tab[longueur - 1] = tampon;
                    permut = true;
                }else {permut = false;}
            }
        } while (permut);
    }

hope that help you.

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