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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

Different between parseInt() and valueOf() in java?

Well, the API for Integer.valueOf(String) does indeed say that the String is interpreted exactly as if it were given to Integer.parseInt(String). However, valueOf(String) returns a new Integer() object whereas parseInt(String) returns a primitive int.

If you want to enjoy the potential caching benefits of Integer.valueOf(int), you could also use this eyesore:

Integer k = Integer.valueOf(Integer.parseInt("123"))

Now, if what you want is the object and not the primitive, then using valueOf(String) may be more attractive than making a new object out of parseInt(String) because the former is consistently present across Integer, Long, Double, etc.

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