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Remove three consecutive duplicates from string

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  • Difficulty Level : Easy
  • Last Updated : 13 Jun, 2022

Given a string, you have to remove the three consecutive duplicates from the string. If no three are consecutive then output the string as it is.
Examples: 
 

Input : aabbbaccddddc
Output :ccdc

Input :aabbaccddc
Output :aabbaccddc

 

Explanation : 
We insert the characters of string one by one to vector and keep on checking the size of vector. If the size of vector is greater than 2, then we will check whether the last 3 characters of the string are same or not. If the characters are same 
then we will move three steps backwards in array using resize() else not. 
 

C++




// C++ program to remove three consecutive
// duplicates
#include <bits/stdc++.h>
using namespace std;
 
// function to remove three consecutive
// duplicates
void remove3ConsecutiveDuplicates(string str)
{
    vector<char> v;
    for (int i = 0; i < str.size(); ++i) {
        v.push_back(str[i]);
 
        if (v.size() > 2) {
            int sz = v.size();
 
            // removing three consecutive duplicates
            if (v[sz - 1] == v[sz - 2] &&
                v[sz - 2] == v[sz - 3]) {
                v.resize(sz - 3); // Removing three characters
                                 // from the string
            }
        }
    }
 
    // printing the string final string
    for (int i = 0; i < v.size(); ++i)
        cout << v[i];
}
 
// driver code
int main()
{
    string str = "aabbbaccddddc";
 
    remove3ConsecutiveDuplicates(str);
    return 0;
}

Java




// Java program to remove three consecutive
// duplicates
import java.util.*;
 
class GFG
{
 
// function to remove three consecutive
// duplicates
static void remove3ConsecutiveDuplicates(String str)
{
    Vector<Character> v = new Vector<>();
    for (int i = 0; i < str.length(); ++i)
    {
        v.add(str.charAt(i));
 
        if (v.size() > 2)
        {
            int sz = v.size();
 
            // removing three consecutive duplicates
            if (v.get(sz - 1) == v.get(sz - 2) &&
                v.get(sz - 2) == v.get(sz - 3))
            {
                v.setSize(sz - 3); // Removing three characters
                                // from the string
            }
        }
    }
 
    // printing the string final string
    for (int i = 0; i < v.size(); ++i)
        System.out.print(v.get(i));
}
 
// Driver code
public static void main(String[] args)
{
    String str = "aabbbaccddddc";
    remove3ConsecutiveDuplicates(str);
}
}
 
// This code contributed by Rajput-Ji

Python3




# Python3 program to remove three consecutive duplicates
 
# function to remove three consecutive duplicates
def remove3ConsecutiveDuplicates(string):
    val = ""
    i = 0
    while (i < len(string)):
        if (i < len(string) - 2 and
            string[i] * 3 == string[i:i + 3]):
            i += 3
        else:
            val += string[i]
            i += 1
             
    if (len(val) == len(string)):
        return val
    else:
        return remove3ConsecutiveDuplicates(val)
 
# Driver code
string = "aabbbaccddddc"
val = remove3ConsecutiveDuplicates(string)
print(val)
 
# This code is contributed by
# Shubham Singh(SHUBHAMSINGH10)

C#




// C# program to remove three consecutive
// duplicates
using System;
using System.Collections.Generic;
 
class GFG
{
 
// function to remove three consecutive
// duplicates
static void remove3ConsecutiveDuplicates(String str)
{
    List<char> v = new List<char>();
    for (int i = 0; i < str.Length; ++i)
    {
        v.Add(str[i]);
 
        if (v.Count > 2)
        {
            int sz = v.Count;
 
            // removing three consecutive duplicates
            if (v[sz - 1] == v[sz - 2] &&
                v[sz - 2] == v[sz - 3])
            {
                v.RemoveRange(sz-3,3); // Removing three characters
                                // from the string
            }
        }
    }
 
    // printing the string final string
    for (int i = 0; i < v.Count; ++i)
        Console.Write(v[i]);
}
 
// Driver code
public static void Main(String[] args)
{
    String str = "aabbbaccddddc";
    remove3ConsecutiveDuplicates(str);
}
}
 
// This code has been contributed by 29AjayKumar

PHP




<?php
// PHP program to remove three consecutive
// duplicates
 
// function to remove three consecutive
// duplicates
function remove3ConsecutiveDuplicates($str)
{
    $v = array();
    for ($i = 0; $i < strlen($str); ++$i)
    {
        array_push($v, $str[$i]);
 
        if (count($v) > 2)
        {
            $sz = count($v);
 
            // removing three consecutive duplicates
            if ($v[$sz - 1] == $v[$sz - 2] &&
                $v[$sz - 2] == $v[$sz - 3])
            {
                array_pop($v);
                array_pop($v);
                array_pop($v);
                // Removing three characters
                                // from the string
            }
        }
    }
 
    // printing the string final string
    for ($i = 0; $i < count($v); ++$i)
        echo $v[$i];
}
 
    // Driver code
    $str = "aabbbaccddddc";
 
    remove3ConsecutiveDuplicates($str);
 
// This code is contributed by mits
?>

Javascript




<script>
// Javascript program to remove three consecutive
// duplicates
 
// function to remove three consecutive
// duplicates
function remove3ConsecutiveDuplicates(str)
{
    let v = [];
    for (let i = 0; i < str.length; ++i)
    {
        v.push(str[i]);
   
        if (v.length > 2)
        {
            let sz = v.length;
   
            // removing three consecutive duplicates
            if (v[sz - 1] == v[sz - 2] &&
                v[sz - 2] == v[sz - 3])
            {
                v.pop();
                v.pop();
                v.pop();
                // Removing three characters
                                // from the string
            }
        }
    }
   
    // printing the string final string
    for (let i = 0; i < v.length; ++i)
        document.write(v[i]);
}
 
// Driver code
let str = "aabbbaccddddc";
remove3ConsecutiveDuplicates(str);
 
// This code is contributed by rag2127
</script>

Output: 
 

ccdc

Time Complexity: O(n)

Auxiliary Space: O(n)

This article is contributed by Roshni Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 


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