Question

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

Answer 1

public class MyClass {
    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 = {-9, 2, 5, 8, -7, 4, 1};

	    System.out.print("equilibrium index = " + getEquilibriumIndex(arr));
    }
}







/*
run:

equilibrium index = 3

*/

 

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