Equilibrium_point.cpp

/*Given an array of integers arr[], the task is to find the first equilibrium point in the array.

The equilibrium point in an array is an index (0-based indexing) such that the sum of all elements before that index is the same as the sum of elements after it. Return -1 if no such point exists. 

Examples:

Input: arr[] = [1, 2, 0, 3]
Output: 2 
Explanation: The sum of left of index 2 is 1 + 2 = 3 and sum on right of index 2 is 3.
Input: arr[] = [1, 1, 1, 1]
Output: -1
Explanation: There is no equilibrium index in the array.
Input: arr[] = [-7, 1, 5, 2, -4, 3, 0]
Output: 3
Explanation: The sum of left of index 3 is -7 + 1 + 5 = -1 and sum on right of index 3 is -4 + 3 + 0 = -1.
*/
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

class Solution {
    public:
      // Function to find equilibrium point in the array.
      int findEquilibrium(vector<int> &arr) {
          // code here
          int left_sum=0;
          int right_sum = 0;
          int index = 1;
          for(int i = 2; i<arr.size();i++)
          {
            right_sum+=arr[i];
          }
          
           left_sum+=arr[0];
          for(int j = 0;j<index && j<arr.size(); j++)
          {
            if(left_sum==right_sum)
            {
                return index;
            }
              
              else
              {
                left_sum+=arr[index];
                index++;
                right_sum-=arr[index];
            }
        }
        return -1;
    }
};