Program to Move zeros to end of integer array in java (example)

• Given an array containing integers (+ve, -ve & 0), we would like to move zeros to end of array.
• We will iterate through the array & we will move zeros to end of array.
• We have discussed similar problems:
  • Segregate array containing even & odd numbers.
  • Dutch national flag problem or sort array containing 0, 1 & 2

1. Example – move zeros to end of array in java (example)

Example 1:

• If input array is { 2, 0, 5, 2, 0, 3, 1 }
• We would like to get output {2, 5, 2, 3, 1, 0, 0}

Example 2:

• If input array is { 1, 0, 2, 3, 0, 4, 0}
• We would like to get output {1, 2, 3, 4, 0, 0, 0}

2. Algorithm – move zeros to end of array in java (example)

• Initialize variable nonZeros=0
  • nonZeros represents number of non zero element in an array
• Iterate through the array ( 0 to length of array).
  • if current element is non zero i.e. inputArray[i] != 0
    • inputArray[nonZeros++] = inputArray[index];
• At end of iteration, all non zero elements are moved to left side of array.
• We will append zeros till the length of array.
• Now, we have successfully move all zeros to end of array.
• Time complexity of algorithm is O (n).

3. Program – move zeros to the end of array in java (example)

package org.learn.arrays;

import java.util.Arrays;

public class MoveZerosToEnd {

 private static void moveZeroToEnd(int[] inputArray) {

  int index = 0;
  int nonZeros = 0;
  int length = inputArray.length;
  while (index < length) {

   if (inputArray[index] != 0) {
    inputArray[nonZeros++] = inputArray[index];
   }
   index++;
  }

  while (nonZeros < length) {
   inputArray[nonZeros++] = 0;
  }
  System.out.printf("%s", Arrays.toString(inputArray));
 }

 public static void main(String[] args) {

  int arr[] = { 2, 0, 5, 2, 0, 3, 1 };
  String sArray = Arrays.toString(arr);
  System.out.printf("1. Move zeros of array %s to end :", sArray);
  moveZeroToEnd(arr);
  
  arr = new int[]{ 1, 0, 2, 3, 0, 4, 0 };
  sArray = Arrays.toString(arr);
  System.out.printf("\n2. Move zeros of array %s to end :", sArray);
  moveZeroToEnd(arr);
 }
}

4. Output – move zeros to the end of array in java (example)

1. Move zeros of array [2, 0, 5, 2, 0, 3, 1] to end :[2, 5, 2, 3, 1, 0, 0]
2. Move zeros of array [1, 0, 2, 3, 0, 4, 0] to end :[1, 2, 3, 4, 0, 0, 0]