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Remove odd indexed characters from a given string
  • Last Updated : 07 Sep, 2020

Given string str of size N, the task is to remove the characters present at odd indices (0-based indexing) of a given string.

Examples : 

Input: str = “abcdef”
Output: ace
Explanation:
The characters ‘b’, ‘d’ and ‘f’ are present at odd indices, i.e. 1, 3 and 5 respectively. Therefore, they are removed from the string.

Input: str = “geeks”
Output: ges

Approach: Follow the steps below to solve the problem:



  • Initialize an empty string, say new_string, to store the result.
  • Traverse the given string and for every index, check if it is even or not.
  • If found to be true, append the characters at those indices to the string new_string.
  • Finally, after complete traversal of the entire string, return the new_string.

Below is the implementation of the above approach:

C++




// C++ program to implement
// the above approach
  
#include <bits/stdc++.h>
using namespace std;
  
// Function to remove the odd
// indexed characters from a given string
string removeOddIndexCharacters(string s)
{
  
    // Stores the resultant string
    string new_string = "";
  
    for (int i = 0; i < s.length(); i++) {
  
        // If current index is odd
        if (i % 2 == 1) {
  
            // Skip the character
            continue;
        }
  
        // Otherwise, append the
        // character
        new_string += s[i];
    }
  
    // Return the result
    return new_string;
}
  
// Driver Code
int main()
{
    string str = "abcdef";
  
    // Function call
    cout << removeOddIndexCharacters(str);
  
    return 0;
}

Java




// Java program to implement
// the above approach
import java.util.*;
  
class GFG {
  
    // Function to remove odd indexed
    // characters from a given string
    static String removeOddIndexCharacters(
        String s)
    {
  
        // Stores the resultant string
        String new_string = "";
  
        for (int i = 0; i < s.length(); i++) {
  
            // If the current index is odd
            if (i % 2 == 1)
  
                // Skip the character
                continue;
  
            // Otherwise, append the
            // character
            new_string += s.charAt(i);
        }
  
        // Return the modified string
        return new_string;
    }
  
    // Driver Code
    public static void main(String[] args)
    {
        String str = "abcdef";
  
        // Remove the characters which
        // have odd index
        str = removeOddIndexCharacters(str);
        System.out.print(str);
    }
}

Python3




# Python3 program to implement
# the above approach
    
# Function to remove the odd
# indexed characters from a given string
def removeOddIndexCharacters(s): 
        
      
      
    # Stores the resultant string 
    new_s = "" 
    
    i = 0
    while i < len(s): 
    
        # If the current index is odd
        if (i % 2 == 1):
          
            # Skip the character
            i+= 1
            continue
    
        # Otherwise, append the 
        # character 
        new_s += s[i]
        i+= 1
          
    
    # Return the modified string 
    return new_s 
    
# Driver Code 
if __name__ == '__main__'
    str = "abcdef"
    
    # Remove the characters which 
    # have odd index 
    str = removeOddIndexCharacters(str
    print(str)

C#




// C# program to implement 
// the above approach 
using System;
  
class GFG{ 
  
// Function to remove odd indexed 
// characters from a given string 
static string removeOddIndexCharacters(string s) 
      
    // Stores the resultant string 
    string new_string = ""
  
    for(int i = 0; i < s.Length; i++)
    
          
        // If the current index is odd 
        if (i % 2 == 1) 
  
            // Skip the character 
            continue
  
        // Otherwise, append the 
        // character 
        new_string += s[i]; 
    
  
    // Return the modified string 
    return new_string; 
  
// Driver Code 
public static void Main() 
    string str = "abcdef"
  
    // Remove the characters which 
    // have odd index 
    str = removeOddIndexCharacters(str); 
      
    Console.Write(str); 
}
  
// This code is contributed by sanjoy_62
Output: 
ace

Time Complexity: O(N)
Auxiliary Space: O(N)

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