Maximum Bitwise AND value of subsequence of length K

// Importing itertools is not necessary in JavaScript

// For storing all bitwise and.
let v = [];

// Recursive function to print all
// possible subsequences for given array
function subsequence(arr, index, subarr, n, k) 
{

  // Calculate the bitwise and when reach
  // at last index
  if (index == n) {
    if (subarr.length == k) {
      let ans = subarr[0];
      for (let i = 1; i < subarr.length; i++) {
        ans &= subarr[i];
      }
      v.push(ans); // Storing the bitwise
      // and to vector v.
    }
    return;
  } else {
    // Pick the current index into the subsequence.
    subarr.push(arr[index]);
    subsequence(arr, index + 1, subarr, n, k);
    subarr.pop();
    
    // Not picking the element into the subsequence.
    subsequence(arr, index + 1, subarr, n, k);
  }
}

// Driver Code
let arr = [255, 127, 31, 5, 24, 37, 15];
let n = arr.length;
let k = 5;
let vec = [];

subsequence(arr, 0, vec, n, k);

// Maximum bitwise and is
console.log(Math.max(...v));

<script>
// Javascript program to find the sum of
// the addition of all possible subsets.

// Function to perform step-1
function findSubset(temp,k)
{
    let ans = [];
  
    // Iterate from left till 0
    // till we get a bit set of K numbers
    for (let i = last; i >= 0; i--)
    {
        let cnt = 0;
  
        // Count the numbers whose
        // i-th bit is set
        for (let it=0;it< temp.length;it++)
        {
            let bit = temp[it] & (1 << i);
            if (bit > 0)
                cnt++;
        }
  
        // If the array has numbers>=k
        // whose i-th bit is set
        if (cnt >= k) 
        {
            for (let it=0;it< temp.length;it++) 
            {
                let bit = temp[it] & (1 << i);
                if (bit > 0)
                    ans.push(temp[it]);
            }
  
            // Update last
            last = i - 1;
  
            // Return the new set of numbers
            return ans;
        }
    }
    return ans;
}

// Function to find the maximum '&' value
// of K elements in subsequence
function findMaxiumAnd(a,n,k)
{
    last = 31;
      
    // Temporary arrays
    let temp1 = [];
    let temp2 = [];
  
    // Initially temp = arr
    for (let i = 0; i < n; i++) 
    {
        temp2.push(a[i]);
    }
  
    // Iterate till we have >=K elements
    while (temp2.length >= k) 
    {
  
        // Temp array
        temp1 = temp2;
  
        // Find new temp array if
        // K elements are there
        temp2 = findSubset(temp2, k);
    }
  
    // Find the & value
    let ans = temp1[0];
    for (let i = 0; i < k; i++)
        ans = ans & temp1[i];
  
    return ans;
}

// Driver Code
let a=[255, 127, 31, 5, 24, 37, 15 ];
let n = a.length;
let k = 4;
document.write(findMaxiumAnd(a, n, k));



// This code is contributed by unknown2108
</script>

// Javascript program to find the sum of
// the addition of all possible subsets.

// function performing calculation
function max_and(N, A, K)
{

    // initializing result with 0 .
    let result = 0;
    for (let j = 31; j >= 0; j--) 
    {
    
        // initializing temp with (result|(1<<j)) .
        let temp = (result | (1 << j));
        
        // initializing count with 0 .
        let count = 0;
        for (let j = 0; j < N; j++) 
        {
        
            // counting the number of element having jth bit
            // set .
            if ((temp & A[j]) == temp) {
                count = count + 1;
            }
        }
        
        // checking if there exist K element with jth bit
        // set.
        if (count >= K)
        {
        
            // updating result with temp.
            result = temp;
        }
    }
    
    // returning result.
    return result;
}

// Given Array A
let A = [ 255, 127, 31, 5, 24, 37 ,15 ];

// Size of Array A .
let N = 7;

// Required Subsequence size
let K = 4;

// calling function performing calculation and printing
// the result.
console.log("Maximum AND of subsequence of A of size K is : ", max_and(N, A, K));

// The code is contributed by Gautam goel.