Problem

Given an array arr consisting of integers ranging from 0 to 9, the task is to remove consecutive duplicates while preserving the order of the remaining elements. For instance, if arr = [1, 1, 3, 3, 0, 1, 1], the result should be [1, 3, 0, 1]. Similarly, for arr = [4, 4, 4, 3, 3], the result should be [4, 3]. Implement the function solution that returns an array containing the elements after removing consecutive duplicates.

Constraints

• The size of the array arr is a natural number less than or equal to 1,000,000.
• Each element of arr is an integer between 0 and 9, inclusive.

Example Inputs and Outputs

How to Approach?

Step1: Initialize variables in loop

Step2: Array copy and sort

Step3: Designate elements to output array

Code

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import java.util.*;

public class Solution {
    public int[] solution(int []arr) {
        Deque<Integer> stack = new ArrayDeque<>();
        stack.push(arr[0]);
        
        for(int i=1; i < arr.length; i++){
            if(stack.peek() != arr[i]){
                stack.push(arr[i]);
            }
        }

        int[] answer = new int[stack.size()];
        
        for(int i=stack.size()-1; i >= 0; i--){
            answer[i] = stack.pop();
        }
        
        return answer;
    }
}