Remove first adjacent pairs of similar characters until possible

Given a string Str, the task is to remove first adjacent pairs of similar characters until we can.

Note: Remove adjacent characters to get a new string and then again remove adjacent duplicates from the new string and keep repeating this process until all similar adjacent character pairs are removed.

Examples:



Input: str = “keexxllx”
Output: kx
Step 0: Remove ee to get “kxxllx”
Step 1: Remove xx to get “kllx”
Step 2: Remove ll to get “kx”

Input: str = “abbaca”
Output: ca

Approach:
Use string’s back() and pop_back() method STL in C++ to solve the above problem. Iterate for every character in the string, and if the adjacent characters are same, then remove the adjacent characters using pop_back() function. At the end, return the final string.

Below is the implementation of the above approach:

C++

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// C++ implementation of the above approach
#include <bits/stdc++.h>
using namespace std;
  
// Function to remove adjacent duplicates
string removeDuplicates(string S)
{
    string ans = "";
  
    // Iterate for every character 
    // in the string
    for (auto it : S) {
  
        // If ans string is empty or its last
        // character does not match with the 
        // current character then append this 
        // character to the string
        if (ans.empty() or ans.back() != it)
            ans.push_back(it);
  
        // Matches with the previous one
        else if (ans.back() == it)
            ans.pop_back();
    }
  
    // Return the answer
    return ans;
}
  
// Driver Code
int main()
{
    string str = "keexxllx";
    cout << removeDuplicates(str);
}

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Java














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// Java implementation of the above approach 


class GFG  


{ 


  


    // Function to remove adjacent duplicates 


    static String removeDuplicates(String S) 


    { 


        String ans = ""; 


  


        // Iterate for every character 


        // in the string 


        for (int i = 0; i < S.length(); i++)  


        { 


  


            // If ans string is empty or its last 


            // character does not match with the 


            // current character then append this 


            // character to the string 


            if (ans.isEmpty() ||  


                ans.charAt(ans.length() - 1) != S.charAt(i)) 


                ans += S.charAt(i); 


  


            // Matches with the previous one 


            else if (ans.charAt(ans.length() - 1) == S.charAt(i)) 


                ans = ans.substring(0, ans.length() - 1); 


        } 


  


        // Return the answer 


        return ans; 


    } 


  


    // Driver Code 


    public static void main(String[] args) 


    { 


        String str = "keexxllx"; 


        System.out.println(removeDuplicates(str)); 


    } 


} 


  


// This code is contributed by 


// sanjeev2552 



















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Python3














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# Python3 implementation of the above approach  


  


# Function to remove adjacent duplicates  


def removeDuplicates(S) :  


  


    ans = "";  


  


    # Iterate for every character  


    # in the string  


    for it in S : 


  


        # If ans string is empty or its last  


        # character does not match with the  


        # current character then append this  


        # character to the string  


        if (ans == "" or ans[-1] != it) : 


            ans += it ;  


  


        # Matches with the previous one  


        elif (ans[-1] == it) : 


            ans = ans[:-1];  


  


    # Return the answer  


    return ans;  


  


  


# Driver Code  


if __name__ == "__main__" : 


  


    string = "keexxllx";  


    print(removeDuplicates(string));  


      


# This code is contributed by AnkitRai01 



















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C#














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// C# implementation of the above approach 


using System; 


      


class GFG  


{ 


  


    // Function to remove adjacent duplicates 


    static String removeDuplicates(String S) 


    { 


        String ans = ""; 


  


        // Iterate for every character 


        // in the string 


        for (int i = 0; i < S.Length; i++)  


        { 


  


            // If ans string is empty or its last 


            // character does not match with the 


            // current character then append this 


            // character to the string 


            if (ans == "" ||  


                ans[ans.Length - 1] != S[i]) 


                ans += S[i]; 


  


            // Matches with the previous one 


            else if (ans[ans.Length - 1] == S[i]) 


                ans = ans.Substring(0, ans.Length - 1); 


        } 


  


        // Return the answer 


        return ans; 


    } 


  


    // Driver Code 


    public static void Main(String[] args) 


    { 


        String str = "keexxllx"; 


        Console.WriteLine(removeDuplicates(str)); 


    } 


} 


  


// This code is contributed by Rajput-Ji 



















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Output:


kx






          
          
          
          

            

    

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    Article Tags : 
C++ Programs
Strings

           	
Practice Tags : 
Strings
STL

        

         

         
 
         
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