Question

Given an array A[] of integers find sum of product of all pairs of array elements

Input:
First line consists of T test cases. First line of every test case consists of N, denoting number of elements of array. Second line consists of elements of array.

Output:
Single line output, print the sum of products.

Constraints:
1<=T<=100
1<=N<=100

Solve the problem using pointers and (if possible) using operators

Example:

Input:
2
3
1 3 4
4
2 3 4 5

Output:
19
71

Answer 1

Answer:

Explanation:

Outer loop is for the number of testcases.

Then in each test case, first using a for loop, n array elements are taken input and stored in array a.

Then using nested for loops, each pair is accessed using pointers(as mentioned above) and sum of products is calculated and printed at the end of test case.

Code:

#include <iostream>

using namespace std;

int main()
{
int t;
cin>>t;
  
for(int k = 0; k<t; k++)
{
int n, sum = 0;
cin>>n;
  
int a[n];
  
for(int i=0; i<n; i++)
{
cin>>a[i];
}
  
for(int i=0; i<n-1; i++)
{
for(int j=i+1; j<n; j++)
{
sum = sum + (*(a+i) * *(a+j));
}
}
  
cout<<sum<<endl;
}

return 0;
}

Output:

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