Check if a given string is made up of two alternating characters

Given a string str, the task is to check whether the given string is made up of only two alternating characters.

Examples:

Input: str = “ABABABAB”
Output: Yes



Input: str = “XYZ”
Output: No

Approach: In order for the string to be made up of only two alternating characters, it must satisfy the following conditions:

  1. All the characters at odd indices must be same.
  2. All the characters at even indices must be same.
  3. str[0] != str[1] (This is because string of type “AAAAA” where a single character is repeated a number of time will also satisfy the above two conditions)

Below is the implementation of the above approach:

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
  
// Function that returns true if the string
// is made up of two alternating characters
bool isTwoAlter(string s)
{
  
    // Check if ith character matches
    // with the character at index (i + 2)
    for (int i = 0; i < s.length() - 2; i++) {
        if (s[i] != s[i + 2]) {
            return false;
        }
    }
  
    // If string consists of a single
    // character repeating itself
    if (s[0] == s[1])
        return false;
  
    return true;
}
  
// Driver code
int main()
{
    string str = "ABAB";
  
    if (isTwoAlter(str))
        cout << "Yes";
    else
        cout << "No";
  
    return 0;
}

chevron_right


Java

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java implementation of the approach
import java.io.*;
  
class GFG
{
  
// Function that returns true if the string
// is made up of two alternating characters
static boolean isTwoAlter(String s)
{
  
    // Check if ith character matches
    // with the character at index (i + 2)
    for (int i = 0; i < s.length() - 2; i++)
    {
        if (s.charAt(i) != s.charAt(i + 2))
        {
            return false;
        }
    }
  
    // If string consists of a single
    // character repeating itself
    if (s.charAt(0) == s.charAt(1))
        return false;
  
    return true;
}
  
// Driver code
public static void main (String[] args) 
{
        String str = "ABAB";
  
    if (isTwoAlter(str))
        System.out.print( "Yes");
    else
        System.out.print("No");
}
}
  
// This code is contributed by anuj_67..

chevron_right


Python 3

filter_none

edit
close

play_arrow

link
brightness_4
code

# Function that returns true if the string
# is made up of two alternating characters
def isTwoAlter( s):
  
    # Check if ith character matches
    # with the character at index (i + 2)
    for i in range ( len( s) - 2) :
        if (s[i] != s[i + 2]) :
            return False
          
      
  
    #If string consists of a single
    #character repeating itself
    if (s[0] == s[1]):
        return False
  
    return True
  
# Driver code
if __name__ == "__main__":
    str = "ABAB"
  
    if (isTwoAlter(str)):
        print ( "Yes")
    else:
        print ("No")
  
# This code is contributed by ChitraNayal

chevron_right


C#

filter_none

edit
close

play_arrow

link
brightness_4
code

// C# implementation of the approach 
using System;
  
class GFG 
  
    // Function that returns true if the string 
    // is made up of two alternating characters 
    static bool isTwoAlter(string s) 
    
      
        // Check if ith character matches 
        // with the character at index (i + 2) 
        for (int i = 0; i < s.Length - 2; i++) 
        
            if (s[i] != s[i +2]) 
            
                return false
            
        
      
        // If string consists of a single 
        // character repeating itself 
        if (s[0] == s[1]) 
            return false
      
        return true
    
      
    // Driver code 
    public static void Main() 
    
            string str = "ABAB"
      
        if (isTwoAlter(str)) 
            Console.WriteLine( "Yes"); 
        else
            Console.WriteLine("No"); 
    
  
// This code is contributed by AnkitRai01

chevron_right


Output:

Yes


My Personal Notes arrow_drop_up

Second year Department of Information Technology Jadavpur University

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.



Improved By : vt_m, AnkitRai01, chitranayal



Article Tags :
Practice Tags :


Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.