# Maximum number of contiguous array elements with same number of set bits

Given an array with n elements. The task is to find the maximum number of contiguous array elements which have the same number of set bits.

Examples:

```Input : arr[] = {14, 1, 2, 32, 12, 10}
Output : 3
Elements 1, 2, 32 have same number of set bits
and are contiguous.

Input : arr[] = {1, 6, 9, 15, 8}
Output : 2
Elements 6, 9 have same number of set bits.
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach:

• Traverse the array from left to right and store the number of set bits of each element in a vector.
• Our task is reduced in finding the longest chain of same elements in this vector.
• Maintain two variables, current_count and max_count. Initialise both of them with 1.
• Traverse the vector and check if current element is same as previous element. If it is same, increment current_count. If it is not same, then reinitialize current_count with 1.
• At each step, max_count must be assigned maximum value between max_count and current_count.
• Final value of max_count is the answer.

Below is the implementation of the above approach:

## C++

 `// C++ program to find the maximum number of ` `// contiguous array elements with same ` `// number of set bits ` `#include ` `using` `namespace` `std; ` ` `  `// Function to find maximum contiguous elements ` `// with same set bits ` `int` `sameSetBits(``int` `arr[], ``int` `n) ` `{ ` `    ``vector<``int``> v; ` ` `  `    ``// Insert number of set bits in each element ` `    ``// of the array to the vector ` `    ``// __builtin_popcount() function returns the number ` `    ``// of set bits in an integer in C++ ` `    ``for` `(``int` `i = 0; i < n; i++) ` `        ``v.push_back(__builtin_popcount(arr[i])); ` ` `  `    ``int` `current_count = 1, max_count = 1; ` ` `  `    ``// Finding the maximum number of same ` `    ``// contiguous elements ` `    ``for` `(``int` `i = 1; i < v.size(); i++) { ` `        ``if` `(v[i + 1] == v[i]) ` `            ``current_count++; ` `        ``else` `            ``current_count = 1; ` ` `  `        ``max_count = max(max_count, current_count); ` `    ``} ` ` `  `    ``// return answer ` `    ``return` `max_count; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `arr[] = { 9, 75, 14, 7, 13, 11 }; ` `    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr[0]); ` ` `  `    ``cout << sameSetBits(arr, n); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to find the maximum  ` `// number of contiguous array elements ` `// with same number of set bits ` `import` `java.io.*; ` `import` `java.util.*; ` ` `  `class` `GFG ` `{ ` `     `  `    ``// Function to find maximum contiguous ` `    ``// elements with same set bits ` `    ``static` `int` `sameSetBits(``int` `arr[], ``int` `n) ` `    ``{ ` `        ``Vector v = ``new` `Vector<>(); ` `     `  `        ``// Insert number of set bits in each element ` `        ``// of the array to the vector ` `                ``for` `(``int` `i = ``0``; i < n; i++) ` `        ``{ ` `            ``int` `count = Integer.bitCount(arr[i]); ` `            ``v.add(count); ` `        ``} ` `     `  `        ``int` `current_count = ``1``, max_count = ``1``; ` `     `  `        ``// Finding the maximum number of same ` `        ``// contiguous elements ` `        ``for` `(``int` `i = ``1``; i < v.size()-``1``; i++) ` `        ``{ ` `            ``if` `(v.get(i + ``1``) == v.get(i)) ` `                ``current_count++; ` `            ``else` `                ``current_count = ``1``; ` `     `  `            ``max_count = Math.max(max_count, current_count); ` `        ``} ` `     `  `        ``// return answer ` `        ``return` `max_count; ` `    ``} ` `     `  `    ``// Driver code ` `    ``public` `static` `void` `main (String[] args)  ` `    ``{ ` `        ``int` `arr[] = { ``9``, ``75``, ``14``, ``7``, ``13``, ``11` `}; ` `        ``int` `n = arr.length; ` `        ``System.out.println(sameSetBits(arr, n)); ` `    ``} ` `} ` ` `  `// This code is contributed by Archana_kumari `

## Python3

 `# Python 3 program to find the maximum  ` `# number of contiguous array elements  ` `# with same number of set bits ` ` `  `# Function to find maximum contiguous ` `# elements with same set bits ` `def` `sameSetBits(arr, n): ` `    ``v ``=` `[] ` ` `  `    ``# Insert number of set bits in each  ` `    ``# element of the array to the vector ` `     `  `    ``# function returns the number of set  ` `    ``# bits in an integer  ` `    ``for` `i ``in` `range``(``0``, n, ``1``): ` `        ``v.append(``bin``(arr[i]).count(``'1'``)) ` ` `  `    ``current_count ``=` `1` `    ``max_count ``=` `1` ` `  `    ``# Finding the maximum number of same ` `    ``# contiguous elements ` `    ``for` `i ``in` `range``(``1``, ``len``(v) ``-` `1``, ``1``): ` `        ``if` `(v[i ``+` `1``] ``=``=` `v[i]): ` `            ``current_count ``+``=` `1` `        ``else``: ` `            ``current_count ``=` `1` ` `  `        ``max_count ``=` `max``(max_count,  ` `                        ``current_count) ` `     `  `    ``# return answer ` `    ``return` `max_count ` ` `  `# Driver code ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``arr ``=` `[``9``, ``75``, ``14``, ``7``, ``13``, ``11``] ` `    ``n ``=` `len``(arr) ` ` `  `    ``print``(sameSetBits(arr, n)) ` ` `  `# This code is contributed by ` `# Surendra_Gangwar `

## C#

 `// C# program to find the maximum  ` `// number of contiguous array elements  ` `// with same number of set bits  ` `using` `System; ` `using` `System.Collections.Generic; ` ` `  `class` `GFG  ` `{  ` `     `  `    ``// Function to find maximum contiguous  ` `    ``// elements with same set bits  ` `    ``static` `int` `sameSetBits(``int` `[]arr, ``int` `n)  ` `    ``{  ` `        ``List<``int``> v = ``new` `List<``int``>();  ` `     `  `        ``// Insert number of set bits in each element  ` `        ``// of the array to the vector  ` `        ``for` `(``int` `i = 0; i < n; i++)  ` `        ``{  ` `            ``int` `count = Bitcount(arr[i]);  ` `            ``v.Add(count);  ` `        ``}  ` `     `  `        ``int` `current_count = 1, max_count = 1;  ` `     `  `        ``// Finding the maximum number of same  ` `        ``// contiguous elements  ` `        ``for` `(``int` `i = 1; i < v.Count-1; i++)  ` `        ``{  ` `            ``if` `(v[i + 1] == v[i])  ` `                ``current_count++;  ` `            ``else` `                ``current_count = 1;  ` `     `  `            ``max_count = Math.Max(max_count, current_count);  ` `        ``}  ` `     `  `        ``// return answer  ` `        ``return` `max_count;  ` `    ``} ` `     `  `    ``static` `int` `Bitcount(``int` `n) ` `    ``{ ` `        ``int` `count = 0; ` `        ``while` `(n != 0) ` `        ``{ ` `            ``count++; ` `            ``n &= (n - 1); ` `        ``} ` `        ``return` `count; ` `    ``}  ` `     `  `    ``// Driver code  ` `    ``public` `static` `void` `Main (String[] args)  ` `    ``{  ` `        ``int` `[]arr = { 9, 75, 14, 7, 13, 11 };  ` `        ``int` `n = arr.Length;  ` `        ``Console.WriteLine(sameSetBits(arr, n));  ` `    ``}  ` `}  ` ` `  `// This code has been contributed by 29AjayKumar `

Output:

```4
```

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