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Maximum length of subarray such that all elements are equal in the subarray

  • Difficulty Level : Basic
  • Last Updated : 16 Apr, 2021

Given an array arr[] of N integers, the task is to find the maximum length subarray that contains similar elements.
Examples: 
 

Input: arr[] = {1, 2, 3, 4, 5, 5, 5, 5, 5, 2, 2, 1, 1} 
Output:
Explanation: 
The subarray {5, 5, 5, 5, 5} has maximum length 5 with identical elements.
Input: arr[] = {1, 2, 3, 4} 
Output:
Explanation: 
All identical element subarray are {1}, {2}, {3}, and {4} which is of length 1. 
 

 

Approach: The idea is to traverse the array store the maximum length and current length of the subarray which has the same elements. Below are the steps: 
 

  1. Traverse the array and check if the current element is equal to the next element then increase the value of the current length variable.
  2. Now, compare the current length with max length to update the maximum length of the subarray.
  3. If the current element is not equal to the next element then reset the length to 1 and continue this for all the elements of the array.

Below is the implementation of the above approach: 
 



C++




// C++ program for the above approach
 
#include <iostream>
using namespace std;
 
// Function to find the longest
// subarray with same element
int longest_subarray(int arr[], int d)
{
 
    int i = 0, j = 1, e = 0;
 
    for (i = 0; i < d - 1; i++) {
 
        // Check if the elements
        // are same then we can
        // increment the length
        if (arr[i] == arr[i + 1]) {
            j = j + 1;
        }
        else {
 
            // Reinitialize j
            j = 1;
        }
 
        // Compare the maximum
        // length e with j
        if (e < j) {
            e = j;
        }
    }
 
    // Return max length
    return e;
}
 
// Driver Code
int main()
{
    // Given array arr[]
    int arr[] = { 1, 2, 3, 4 };
 
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // Function Call
    cout << longest_subarray(arr, N);
}

Java




// Java program for the above approach
import java.util.*;
 
class GFG{
 
// Function to find the longest
// subarray with same element
static int longest_subarray(int arr[], int d)
{
    int i = 0, j = 1, e = 0;
 
    for(i = 0; i < d - 1; i++)
    {
         
       // Check if the elements
       // are same then we can
       // increment the length
       if (arr[i] == arr[i + 1])
       {
           j = j + 1;
       }
       else
       {
            
           // Reinitialize j
           j = 1;
       }
        
       // Compare the maximum
       // length e with j
       if (e < j)
       {
           e = j;
       }
    }
 
    // Return max length
    return e;
}
 
// Driver Code
public static void main(String[] args)
{
     
    // Given array arr[]
    int arr[] = { 1, 2, 3, 4 };
    int N = arr.length;
 
    // Function Call
    System.out.print(longest_subarray(arr, N));
}
}
 
// This code is contributed by 29AjayKumar

Python3




# Python3 program for the above approach
 
# Function to find the longest
# subarray with same element
def longest_subarray(arr, d):
     
    (i, j, e) = (0, 1, 0)
     
    for i in range(d - 1):
         
        # Check if the elements
        # are same then we can
        # increment the length
        if arr[i] == arr[i + 1]:
            j += 1
        else:
             
            # Reinitialize j
            j = 1
         
        # Compare the maximum
        # length e with j
        if e < j:
            e = j
     
    # Return max length
    return e
 
# Driver code
 
# Given list arr[]
arr = [ 1, 2, 3, 4 ]
N = len(arr)
 
# Function call
print(longest_subarray(arr, N))
 
# This code is contributed by rutvik_56

C#




// C# program for the above approach
using System;
 
class GFG{
  
// Function to find the longest
// subarray with same element
static int longest_subarray(int []arr, int d)
{
    int i = 0, j = 1, e = 0;
  
    for(i = 0; i < d - 1; i++)
    {
          
       // Check if the elements
       // are same then we can
       // increment the length
       if (arr[i] == arr[i + 1])
       {
           j = j + 1;
       }
       else
       {
             
           // Reinitialize j
           j = 1;
       }
         
       // Compare the maximum
       // length e with j
       if (e < j)
       {
           e = j;
       }
    }
  
    // Return max length
    return e;
}
  
// Driver Code
public static void Main(String[] args)
{
      
    // Given array []arr
    int []arr = { 1, 2, 3, 4 };
    int N = arr.Length;
  
    // Function Call
    Console.Write(longest_subarray(arr, N));
}
}
 
// This code is contributed by 29AjayKumar

Javascript




<script>
// javascript program for the above approach
 
    // Function to find the longest
    // subarray with same element
    function longest_subarray(arr , d)
    {
        var i = 0, j = 1, e = 0;
 
        for (i = 0; i < d - 1; i++)
        {
 
            // Check if the elements
            // are same then we can
            // increment the length
            if (arr[i] == arr[i + 1])
            {
                j = j + 1;
            }
            else
            {
 
                // Reinitialize j
                j = 1;
            }
 
            // Compare the maximum
            // length e with j
            if (e < j) {
                e = j;
            }
        }
 
        // Return max length
        return e;
    }
 
    // Driver Code
     
        // Given array arr
        var arr = [ 1, 2, 3, 4 ];
        var N = arr.length;
 
        // Function Call
        document.write(longest_subarray(arr, N));
 
// This code is contributed by todaysgaurav
</script>
Output: 
1

 

Time Complexity: O(N) 
Auxiliary Space: O(1)
 

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