RemoveConsecutiveDuplicate.java

package com.interview.string;

/**
 * Remove consecutive duplicate characters
 * e.g
 * AABBCDDAAB -> ABCDAB
 * ABBBCCD -> ABCD
 * Test cases
 * Empty string
 * all unique
 * all duplicates
 * duplicates at certain different places
 */
public class RemoveConsecutiveDuplicate {

    public int removeDuplicates(char input[]){
        int slow = 0;
        int fast = 0;
        int index = 0;
        while(fast < input.length){
            while(fast < input.length && input[slow] == input[fast]){
                fast++;
            }
            input[index++] = input[slow];
            slow = fast;
        }
        return index;
    }
    
    public static void main(String args[]){
        String str = "AAABBCCDDDEFGH";
        char input[] = str.toCharArray();
        RemoveConsecutiveDuplicate rcd = new RemoveConsecutiveDuplicate();
        int len = rcd.removeDuplicates(input);
        for(int i=0; i < len; i++){
            System.out.print(input[i] + " ");
        }
    }
}