Question

How to find the equilibrium index of an array (sum arr[0 to index - 1] == sum arr[index + 1 to size]) in C#

Answer 1

using System;

public class Program
{
	private static int getEquilibriumIndex(int[] arr) {
		int sum_arr = 0;
		int left_part_sum = 0;
		int size = arr.Length;

		for (int i = 0; i < size; i++) {
			sum_arr += arr[i];
		}

		for (int i = 0; i < size; i++) {
			sum_arr -= arr[i];

			if (left_part_sum == sum_arr) {
				return i;
			}

			left_part_sum += arr[i];
		}

		return -1;
	}

	public static void Main(string[] args)
	{
		int[] arr = new int[] {-9, 2, 5, 8, -7, 4, 1};

		Console.Write("equilibrium index = " + getEquilibriumIndex(arr));
	}
}







/*
run:
 
equilibrium index = 3
 
*/

 

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