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Java Array Exercises: Find the equilibrium indices from a given array of integers

Java Array: Exercise-62 with Solution

Write a Java program to find the equilibrium indices from a given array of integers.

An equilibrium index of a sequence is an index into the sequence such that the sum of elements at lower indices is equal to the sum of elements at higher indices.

For example, in a sequence A:
  A0 = -7
  A1 = 1
  A2 = 5
  A3 = 2
  A4 = -4
  A5 = 3
  A6 = 0
3 is an equilibrium index, because:

  A0 + A1 + A2 = A4 + A5 + A6
  
6 is also an equilibrium index, because:

  A0 + A1 + A2 + A3 + A4 + A5 = 0
  
(sum of zero elements is zero)

7 is not an equilibrium index, because it is not a valid index of sequence A.

Example:
Input :
nums = {-7, 1, 5, 2, -4, 3, 0}
Output:
Equilibrium indices found at : 3
Equilibrium indices found at : 6
Source: https://bit.ly/2ziUROQ

Sample Solution:

Java Code:

import java.util.Arrays; 
public class solution {
	public static void main(String[] args) {
		int[] nums = {-7, 1, 5, 2, -4, 3, 0};
		System.out.println("Original array: "+Arrays.toString(nums));
		equlibrium_indices(nums);
	}
 
	public static void equlibrium_indices(int[] nums){
		//find total sum
		int totalSum = 0;
		for (int n : nums) {
			totalSum += n;
		}
		//compare running sum to remaining sum to find equlibrium indices
		int runningSum = 0;
		for (int i = 0; i < nums.length; i++) {
			int n = nums[i];
			if (totalSum - runningSum - n == runningSum) {
				System.out.println("Equilibrium indices found at : "+i);
			}
			runningSum += n;
		}
	}
}

Sample Output:

Original array: [-7, 1, 5, 2, -4, 3, 0]
Equilibrium indices found at : 3
Equilibrium indices found at : 6

Flowchart:

Flowchart: Find the equilibrium indices from a given array of integers

Java Code Editor:

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Previous: Write a Java program to rearrange a given array of unique elements such that every second element of the array is greater than its left and right elements.
Next: Write a Java program to replace each element of the array with product of every other element in a given array of integers.

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Java: Tips of the Day

countOccurrences

Counts the occurrences of a value in an array.

Use Arrays.stream().filter().count() to count total number of values that equals the specified value.

public static long countOccurrences(int[] numbers, int value) {
    return Arrays.stream(numbers)
            .filter(number -> number == value)
            .count();
}

Ref: https://bit.ly/3kCAgLb