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Given an integer array of size N, print the sum of first and last number, second first and second last number and so on.

Note: N is always even.

Boundary Condition:
1<= N <= 9999

Input Format:
The first line contains the size of the array N
The second line contains N integers separated by space.

Output Format:
The first line contains the output as specified.

Example Input/Output 1:
Input:
6
2 9 1 5 3 2

Output:
4 12 6

Example Input/Output 2:
Input:
10
97 94 66 99 17 78 70 44 67 86

Output:
183 161 110 169 95

What I have tried:

C++
#include<stdio.h>
#include <stdlib.h>

int main()
{
    int i,j,n,a[9999],b[9999];
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
    }
    for(i=0;i<n;i++)
    for(j=n-1;j>=0;j--)
    {
    b[i]=a[i]+a[j];
    }
    for(i=0;i<n;i++)
    printf("%d ",b[i]);


}
Posted
Updated 22-Feb-18 9:47am
v2

You do not need two nested for loops, but rather a single loop with two variables.
C
int i, j;
for (i = 0, j = N - 1; i <= j; ++i, --j)
   b[i] = a[i] + a[j];
 
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Comments
CPallini 22-Feb-18 6:50am    
5.
Maciej Los 22-Feb-18 16:12pm    
5ed!
Quote:
i am getting addtionaly 3 zeros in the output

Because you need to correct the printing part too.
C++
for(i=0;i<n/2;i++)
    printf("%d ",b[i]);


[Update]
A little analyze show that a is never reused once b is calculated => you don't need b
C++
#include<stdio.h>
#include <stdlib.h>

int main()
{
    int i,j,n,a[9999],b[9999];
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
    }
    for(i=0,j=n-1;i<j;i++,j--)
    {
        b[i]=a[i]+a[j];
        a[i]=a[i]+a[j];
    }
    for(i=0;i<n/2;i++)
        printf("%d ",b[i]);
        printf("%d ",a[i]);
}

the memory footprint have just been divided by 2 and it is possible to go further.
 
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v2
Comments
Maciej Los 22-Feb-18 16:12pm    
Nice!
#include<stdio.h>
#include <stdlib.h>

int main()
{
int i,n,a[9999],b[9999];
scanf("%d",&n);
for(i=0;i<n;i++)
{
scanf("%d",&a[i]);
}
for(i=0;i<n/2;i++)
{
int j=i-n-1;
b[i]=a[i]+a[j];
}
for(i=0;i<n/2;i++)
printf("%d ",b[i]);
return 0;
}
 
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Comments
Maciej Los 22-Feb-18 16:12pm    
And?

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