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

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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++

// 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); 
} 

Python3

# 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 

Output:

kx

My Personal Notes

Suggest a Topic

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Python3

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