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

Last Updated : 15 Nov, 2022

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.

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 <bits/stdc++.h> 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<Integer> 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# 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

JavaScript

<script>  // Javascript program to find the maximum number of // contiguous array elements with same // number of set bits  function Bitcount(n) {     var count = 0;     while (n != 0)     {         count++;         n &= (n - 1);     }     return count; }   // Function to find maximum contiguous elements // with same set bits function sameSetBits(arr, n) {     var v = [];      // Insert number of set bits in each element     // of the array to the vector     // Bitcount function returns the number     // of set bits in an integer in C++     for (var i = 0; i < n; i++)         v.push(Bitcount(arr[i]));      var current_count = 1, max_count = 1;      // Finding the maximum number of same     // contiguous elements     for (var i = 1; i < v.length; 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; }  // Driver code var arr = [ 9, 75, 14, 7, 13, 11 ]; var n = arr.length; document.write( sameSetBits(arr, n));  </script>

Output

Time Complexity: O(n), since __builtin_popcount has a maximum complexity of 32 for each int value.
Auxiliary Space: O(n)

Count of pairs in an Array with same number of set bits

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

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