Skip to content
Related Articles

Related Articles

Table of Contents

Improve Article
Save Article
Like Article

Length of the longest substring with no consecutive same letters

  • Difficulty Level : Medium
  • Last Updated : 26 Oct, 2021

Given a string str, the task is to find the length of the longest sub-string which does not have any pair of consecutive same characters. 
Examples: 
 

Input: str = “abcdde” 
Output: 4 
“abcd” is the longest
Input: str = “ccccdeededff” 
Output: 5 
“ededf” is the longest 
 

 

Approach: The following steps can be followed to solve the above problem: 
 

  • Initialize cnt and maxi as 1 initially, since this is the minimum answer of the length of the longest answer.
  • Iterate in the string from 1 to n – 1 and increment cnt by 1 if str[i] != str[i – 1].
  • If str[i] == str[i – 1], then re-initialize cnt as 1 and maxi to max(maxi, cnt).

Below is the implementation of the above approach: 
 

C++




// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to return the length
// of the required sub-string
int longestSubstring(string s)
{
    int cnt = 1;
    int maxi = 1;
 
    // Get the length of the string
    int n = s.length();
 
    // Iterate in the string
    for (int i = 1; i < n; i++) {
 
        // Check for not consecutive
        if (s[i] != s[i - 1])
            cnt++;
        else {
 
            // If cnt greater than maxi
            maxi = max(cnt, maxi);
 
            // Re-initialize
            cnt = 1;
        }
    }
 
    // Check after iteration
    // is complete
    maxi = max(cnt, maxi);
 
    return maxi;
}
 
// Driver code
int main()
{
    string s = "ccccdeededff";
    cout << longestSubstring(s);
 
    return 0;
}
Java



// Java implementation of the approach
import java.lang.Math;
 
class GfG
{
 
    // Function to return the length
    // of the required sub-string
    static int longestSubstring(String s)
    {
        int cnt = 1, maxi = 1;
     
        // Get the length of the string
        int n = s.length();
     
        // Iterate in the string
        for (int i = 1; i < n; i++)
        {
     
            // Check for not consecutive
            if (s.charAt(i) != s.charAt(i-1))
                cnt++;
            else
            {
     
                // If cnt greater than maxi
                maxi = Math.max(cnt, maxi);
     
                // Re-initialize
                cnt = 1;
            }
        }
     
        // Check after iteration is complete
        maxi = Math.max(cnt, maxi);
     
        return maxi;
    }
 
    // Driver code
    public static void main(String []args)
    {
         
        String s = "ccccdeededff";
        System.out.println(longestSubstring(s));
    }
}
 
// This code is contributed by Rituraj Jain
C#



// C# implementation of the approach
using System;
 
class GfG
{
 
    // Function to return the length
    // of the required sub-string
    static int longestSubstring(string s)
    {
        int cnt = 1, maxi = 1;
     
        // Get the length of the string
        int n = s.Length;
     
        // Iterate in the string
        for (int i = 1; i < n; i++)
        {
     
            // Check for not consecutive
            if (s[i] != s[i - 1])
                cnt++;
            else
            {
     
                // If cnt greater than maxi
                maxi = Math.Max(cnt, maxi);
     
                // Re-initialize
                cnt = 1;
            }
        }
     
        // Check after iteration is complete
        maxi = Math.Max(cnt, maxi);
     
        return maxi;
    }
 
    // Driver code
    static void Main()
    {
         
        string s = "ccccdeededff";
        Console.WriteLine(longestSubstring(s));
    }
}
 
// This code is contributed by mits
Python3



# Python3 implementation of the approach
 
# Function to return the length
# of the required sub-string
def longestSubstring(s) :
 
    cnt = 1;
    maxi = 1;
 
    # Get the length of the string
    n = len(s);
 
    # Iterate in the string
    for i in range(1, n) :
 
        # Check for not consecutive
        if (s[i] != s[i - 1]) :
            cnt += 1;
             
        else :
             
            # If cnt greater than maxi
            maxi = max(cnt, maxi);
 
            # Re-initialize
            cnt = 1;
 
    # Check after iteration
    # is complete
    maxi = max(cnt, maxi);
 
    return maxi;
 
# Driver code
if __name__ == "__main__" :
     
    s = "ccccdeededff";
    print(longestSubstring(s));
     
# This code is contributed by Ryuga
PHP



<?php
// PHP implementation of the approach
 
// Function to return the length
// of the required sub-string
function longestSubstring($s)
{
    $cnt = 1;
    $maxi = 1;
 
    // Get the length of the string
    $n = strlen($s);
 
    // Iterate in the string
    for ($i = 1; $i < $n; $i++)
    {
 
        // Check for not consecutive
        if ($s[$i] != $s[$i - 1])
            $cnt++;
        else
        {
 
            // If cnt greater than maxi
            $maxi = max($cnt, $maxi);
 
            // Re-initialize
            $cnt = 1;
        }
    }
 
    // Check after iteration
    // is complete
    $maxi = max($cnt, $maxi);
 
    return $maxi;
}
 
// Driver code
$s = "ccccdeededff";
echo longestSubstring($s);
 
// This code is contributed by Akanksha Rai
?>
Javascript



<script>
// javascript implementation of the approach class GfG
 
// Function to return the length
// of the required sub-string
function longestSubstring(s)
{
    var cnt = 1, maxi = 1;
 
    // Get the length of the string
    var n = s.length;
 
    // Iterate in the string
    for (i = 1; i < n; i++)
    {
 
        // Check for not consecutive
        if (s.charAt(i) != s.charAt(i-1))
            cnt++;
        else
        {
 
            // If cnt greater than maxi
            maxi = Math.max(cnt, maxi);
 
            // Re-initialize
            cnt = 1;
        }
    }
 
    // Check after iteration is complete
    maxi = Math.max(cnt, maxi);
 
    return maxi;
}
 
// Driver code
var s = "ccccdeededff";
document.write(longestSubstring(s));
 
 
// This code contributed by shikhasingrajput
</script>
Output: 
5
 

My Personal Notes
arrow_drop_up
Next

Length of the longest substring without repeating characters
Recommended Articles
Page :
Construct a string of length L such that each substring of length X has exactly Y distinct letters
30, Apr 20
Longest substring such that no three consecutive characters are same
17, Sep 19
Longest Even Length Substring such that Sum of First and Second Half is same
19, Dec 14
Generate an N-length string having longest palindromic substring of length K
14, Dec 20
Check if the string contains consecutive letters and each letter occurs exactly once
03, Apr 19
Lexicographically smallest String using all of the first K letters of alphabet and no two adjacent characters are same
10, Feb 22
Length of longest Palindromic Subsequence of even length with no two adjacent characters same
04, Feb 20
Longest substring whose any non-empty substring not prefix or suffix of given String
29, Mar 22
Smallest Greater (than S) String of length K whose letters are subset of S
09, Dec 18
Length of the largest substring which have character with frequency greater than or equal to half of the substring
29, May 19
Minimum length of substring whose rotation generates a palindromic substring
21, May 20
Longest substring of vowels with no two adjacent alphabets same
18, Jun 20
Longest subsequence such that no 3 consecutive characters are same
14, Dec 21
Count possible binary strings of length N without P consecutive 0s and Q consecutive 1s
09, Oct 20
Length of the longest valid substring
29, Sep 15
Length of the longest substring with equal 1s and 0s
25, Oct 17
Length of the longest substring that do not contain any palindrome
08, May 19
Length of longest substring having all characters as K
16, Jul 19
Find length of longest substring with at most K normal characters
26, Apr 20
Length of longest substring to be deleted to make a string equal to another string
15, Sep 20
Length of Longest Palindrome Substring
30, Sep 20
Length of the longest substring with every character appearing even number of times
01, Nov 20
Minimize count of 0s required to be removed to maximize length of longest substring of 1s
22, Jan 21
Length of the longest substring that contains even number of vowels
17, Jun 21
Article Contributed By :
https://media.geeksforgeeks.org/auth/avatar.png
Striver
@Striver
Vote for difficulty
Current difficulty :
Medium





Improved By :
Article Tags :
Practice Tags :
Report Issue

We use cookies to ensure you have the best browsing experience on our website. By using our site, you
acknowledge that you have read and understood our
Cookie Policy &
        Privacy Policy

Lightbox

Start Your Coding Journey Now!