SPOJ Problem ABSP1 Solution in (C++)

Welcome:

The question to the problem can be found here:


Explanation:
1.Notice the array is sorted already.
2. It can be solved with simple Math.
3. There are two logic only.
4. Multiply each element  i -th times(i-th times: position of element in the array)
5. Multiply each element n-1-i -th times.
6. Subtract 4 and 5.
7.Happy Coding !

Code:

#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)

using namespace std;

long long ABS(long long a[],long long n){
    long long sum=0;
rep(i,n){
sum += (a[i]*i) - (a[i]*(n-1-i));
}
return sum;
}
int main(){
 //   freopen("input.txt","r",stdin);
 //freopen("output.txt","w",stdout);
int t;
long long arr[10000];
cin>>t;
while(t-->0){
long long n;
cin>>n;
rep(i,n){
    cin>>arr[i];
}
cout<<ABS(arr,n)<<endl;

}

return 0;}