AP2 - AP - Complete The Series (Easy) ediorial SPOJ - UCS

The link for the problem  AP2 - AP - Complete The Series (Easy) is:

http://www.spoj.com/problems/AP2/

The logic used in this problem  AP2 - AP - Complete The Series (Easy) is:

This problem is used AP formulas.We have A[3] and A[N-3] and Sum of Series (S) in the given input.But we don't know about N and we need to calculate it.

We know the sum of Series of AP: ((A[1]+A[N]/2)*N 

Given A[3] which is equal to
A[3]=A[1]+2*D

So A[1] = A[3] - 2*D

and A[N] is given by A[N] = A[N-2] + 2*DSo ((A[1]+A[N]/2)*N  becomes :
S = ((A[3]-2*D+A[N-2]+2*D)/2)*N

In this, we can know the value of N by:
 N=2*S/(A[3]+A[N-2])

For Finding D in these formulas we have to use the thing:

suppose consider the series for example:

3 6 9 12 15 18 21 24

Suppose we know A[3] 9 and A[N-2] 18 So to find the D for this we must use the formula:

A[N-2]-A[3]/(No of terms in between them +1)

The following is CPP solution for this  "AP2 - AP - Complete The Series (Easy)" is:

#include<iostream>
#include<cstdio>
#define LL long long int
using namespace std;

int main()
{
        int T;
        cin>>T;
        while(T--)
        {
                LL a3,an3,sum,d,n,a;
                cin>>a3>>an3>>sum;
                n = (2*sum)/(a3+an3);
                d = (an3-a3)/(n-5);
                a = a3-(2*d);
                cout<<n<<endl;
                for(int i=0;i<n;i++)
                cout<<(a+(i*d))<<" ";
                cout<<endl;
        }
        return 0;
}

Happy Coding........