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Maximum consecutive repeating character in string

  • Difficulty Level : Easy
  • Last Updated : 10 May, 2021

Given a string, the task is to find the maximum consecutive repeating character in a string.
Note: We do not need to consider the overall count, but the count of repeating that appears in one place.
Examples: 
 

Input : str = "geeekk"
Output : e

Input : str = "aaaabbcbbb"
Output : a

 

The simple solution to this problem is to use two for loops. The outer loop considers the current character, the inner loop counts occurrences of the current character. If the count goes beyond the current maximum count, we update the result. 
 

C++




// C++ program to find the maximum consecutive
// repeating character in given string
#include<bits/stdc++.h>
using namespace std;
 
// function to find out the maximum repeating
// character in given string
char maxRepeating(string str)
{
    int len = str.length();
    int count = 0;
 
    // Find the maximum repeating character
    // starting from str[i]
    char res = str[0];
    for (int i=0; i<len; i++)
    {
        int cur_count = 1;
        for (int j=i+1; j<len; j++)
        {
            if (str[i] != str[j])
                break;
            cur_count++;
        }
 
        // Update result if required
        if (cur_count > count)
        {
            count = cur_count;
            res = str[i];
        }
    }
    return res;
}
 
// Driver code
int main()
{
 
    string str = "aaaabbaaccde";
    cout << maxRepeating(str);
    return 0;
}

Java




// Java program to find the maximum consecutive
// repeating character in given string
public class GFG {
     
    // function to find out the maximum repeating
    // character in given string
    static char maxRepeating(String str)
    {
        int len = str.length();
        int count = 0;
 
        // Find the maximum repeating character
        // starting from str[i]
        char res = str.charAt(0);
        for (int i=0; i<len; i++)
        {
            int cur_count = 1;
            for (int j=i+1; j<len; j++)
            {
                if (str.charAt(i) != str.charAt(j))
                    break;
                cur_count++;
            }
 
            // Update result if required
            if (cur_count > count)
            {
                count = cur_count;
                res = str.charAt(i);
            }
        }
        return res;
    }
 
    // Driver code
    public static void main(String args[])
    {
 
        String str = "aaaabbaaccde";
        System.out.println(maxRepeating(str));
    }
}
// This code is contributed by Sumit Ghosh

Python 3




# Python 3 program to find the
# maximum consecutive repeating
# character in given string
 
# function to find out the maximum
# repeating character in given string
def maxRepeating(str):
 
    l = len(str)
    count = 0
 
    # Find the maximum repeating
    # character starting from str[i]
    res = str[0]
    for i in range(l):
         
        cur_count = 1
        for j in range(i + 1, l):
     
            if (str[i] != str[j]):
                break
            cur_count += 1
 
        # Update result if required
        if cur_count > count :
            count = cur_count
            res = str[i]
    return res
 
# Driver code
if __name__ == "__main__":
 
    str = "aaaabbaaccde"
    print(maxRepeating(str))
 
# This code is contributed
# by ChitraNayal

C#




// C# program to find the maximum
// consecutive repeating character
// in given string
using System;
 
class GFG
{
 
// function to find out the maximum
// repeating character in given string
static char maxRepeating(string str)
{
    int len = str.Length;
    int count = 0;
    char res = str[0];
     
    // Find the maximum repeating
    // character starting from str[i]
    for (int i = 0; i < len; i++)
    {
        int cur_count = 1;
        for (int j = i + 1; j < len; j++)
        {
            if (str[i] != str[j])
                break;
            cur_count++;
        }
 
        // Update result if required
        if (cur_count > count)
        {
            count = cur_count;
            res = str[i];
        }
    }
    return res;
}
 
// Driver code
public static void Main()
{
    string str = "aaaabbaaccde";
    Console.Write(maxRepeating(str));
}
}
 
// This code is contributed
// by ChitraNayal

PHP




<?php
//PHP program to find the maximum consecutive
// repeating character in given string
 
// function to find out the maximum repeating
// character in given string
function  maxRepeating( $str)
{
     $len = strlen($str);
    $count = 0;
      
    // Find the maximum repeating character
    // starting from str[i]
     $res = $str[0];
    for ($i = 0; $i < $len; $i++)
    {
         $cur_count = 1;
        for ($j = $i+1; $j < $len; $j++)
        {
            if ($str[$i] != $str[$j])
                break;
            $cur_count++;
        }
 
        // Update result if required
        if ($cur_count > $count)
        {
            $count = $cur_count;
            $res = $str[$i];
        }
    }
    return $res;
}
 
// Driver code
    $str = "aaaabbaaccde";
    echo  maxRepeating($str);
 
// This code is contributed by ajit
?>

Javascript




<script>
 
// Javascript program to find the maximum consecutive
// repeating character in given string
     
    // function to find out the maximum repeating
    // character in given string
    function maxRepeating(str)
    {
        let len = str.length;
        let count = 0;
   
        // Find the maximum repeating character
        // starting from str[i]
        let res = str[0];
        for (let i=0; i<len; i++)
        {
            let cur_count = 1;
            for (let j=i+1; j<len; j++)
            {
                if (str[i] != str[j])
                    break;
                cur_count++;
            }
   
            // Update result if required
            if (cur_count > count)
            {
                count = cur_count;
                res = str[i];
            }
        }
        return res;
    }
     
    // Driver code
    let str = "aaaabbaaccde";
    document.write(maxRepeating(str));
     
    // This code is contributed by rag2127
 
</script>

Output: 

a

Time Complexity : O(n^2) 
Space Complexity : O(1)
An efficient solution is to run only one loop. The idea is to reset the count as 1 as soon as we find a character not matching with the previous. 
 



C++




// C++ program to find the maximum consecutive
// repeating character in given string
#include<bits/stdc++.h>
using namespace std;
 
// Returns the maximum repeating character in a
// given string
char maxRepeating(string str)
{
    int n = str.length();
    int count = 0;
    char res = str[0];
    int cur_count = 1;
 
    // Traverse string except last character
    for (int i=0; i<n; i++)
    {
        // If current character matches with next
        if (i < n-1 && str[i] == str[i+1])
            cur_count++;
 
        // If doesn't match, update result
        // (if required) and reset count
        else
        {
            if (cur_count > count)
            {
                count = cur_count;
                res = str[i];
            }
            cur_count = 1;
        }
    }
 
    return res;
}
 
// Driver code
int main()
{
    string str = "aaaabbaaccde";
    cout << maxRepeating(str);
    return 0;
}

Java




// Java program to find the maximum consecutive
// repeating character in given string
class GFG {
     
    // function to find out the maximum repeating
    // character in given string
    static char maxRepeating(String str)
    {
        int n = str.length();
        int count = 0;
        char res = str.charAt(0);
        int cur_count = 1;
 
        // Traverse string except last character
        for (int i = 0; i < n; i++)
        {
            // If current character matches with next
            if (i < n - 1 && str.charAt(i) == str.charAt(i + 1))
                cur_count++;
 
            // If doesn't match, update result
            // (if required) and reset count
            else
            {
                if (cur_count > count)
                {
                    count = cur_count;
                    res = str.charAt(i);
                }
                cur_count = 1;
            }
        }
        return res;
    }
 
    // Driver code
    public static void main(String args[])
    {
        String str = "aaaabbaaccde";
        System.out.println(maxRepeating(str));
    }
}
 
// This code is contributed by Sudeep Mukherjee

Python 3




# Python 3 program to find the
# maximum consecutive repeating
# character in given string
 
# Returns the maximum repeating
# character in a given string
def maxRepeating(str):
 
    n = len(str)
    count = 0
    res = str[0]
    cur_count = 1
 
    # Traverse string except
    # last character
    for i in range(n):
         
        # If current character
        # matches with next
        if (i < n - 1 and
            str[i] == str[i + 1]):
            cur_count += 1
 
        # If doesn't match, update result
        # (if required) and reset count
        else:
            if cur_count > count:
                count = cur_count
                res = str[i]
            cur_count = 1
    return res
 
# Driver code
if __name__ == "__main__":
    str = "aaaabbaaccde"
    print(maxRepeating(str))
 
# This code is contributed
# by ChitraNayal

C#




// C# program to find the maximum
// consecutive repeating character
// in given string
using System;
 
class GFG
{
 
// function to find out the
// maximum repeating character
// in given string
static char maxRepeating(string str)
{
    int n = str.Length;
    int count = 0;
    char res = str[0];
    int cur_count = 1;
 
    // Traverse string except
    // last character
    for (int i = 0; i < n; i++)
    {
        // If current character
        // matches with next
        if (i < n - 1 &&
            str[i] == str[i + 1])
            cur_count++;
 
        // If doesn't match, update result
        // (if required) and reset count
        else
        {
            if (cur_count > count)
            {
                count = cur_count;
                res = str[i];
            }
            cur_count = 1;
        }
    }
    return res;
}
 
// Driver code
public static void Main()
{
    string str = "aaaabbaaccde";
    Console.Write(maxRepeating(str));
}
}
 
// This code is contributed
// by ChitraNayal

PHP




<?php
// PHP program to find the maximum
// consecutive repeating character
// in given string
 
// Returns the maximum repeating
// character in a given string
function maxRepeating($str)
{
    $n = strlen($str);
    $count = 0;
    $res = $str[0];
    $cur_count = 1;
 
    // Traverse string except
    // last character
    for ($i = 0; $i < $n; $i++)
    {
        // If current character
        // matches with next
        if ($i < $n - 1 &&
            $str[$i] == $str[$i + 1])
            $cur_count++;
 
        // If doesn't match, update result
        // (if required) and reset count
        else
        {
            if ($cur_count > $count)
            {
                $count = $cur_count;
                $res = $str[$i];
            }
            $cur_count = 1;
        }
    }
 
    return $res;
}
 
// Driver code
$str = "aaaabbaaccde";
echo maxRepeating($str);
 
// This code is contributed
// by ChitraNayal
?>

Javascript




<script>
 
// JavaScript program to find the maximum consecutive
// repeating character in given string
 
  // function to find out the maximum repeating
  // character in given string
function maxRepeating( str)
{
    var n = str.length;
    var count = 0;
    var res = str[0];
    var cur_count = 1;
 
    // Traverse string except last character
    for (var i=0; i<n; i++)
    {
        // If current character matches with next
        if (i < n-1 && str[i] == str[i+1])
            cur_count++;
 
        // If doesn't match, update result
        // (if required) and reset count
        else
        {
            if (cur_count > count)
            {
                count = cur_count;
                res = str[i];
            }
            cur_count = 1;
        }
    }
 
    return res;
}
 
var str = "aaaabbaaccde";
    document.write( maxRepeating(str));
 
</script>

Output:  

a

Time Complexity : O(n) 
Space Complexity : O(1)
This article is contributed by DANISH_RAZA . If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 

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