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Javascript Program to Find k maximum elements of array in original order

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  • Last Updated : 28 May, 2022

Given an array arr[] and an integer k, we need to print k maximum elements of given array. The elements should printed in the order of the input.
Note : k is always less than or equal to n.

Examples:  

Input : arr[] = {10 50 30 60 15}
        k = 2
Output : 50 60
The top 2 elements are printed
as per their appearance in original
array.

Input : arr[] = {50 8 45 12 25 40 84}
            k = 3
Output : 50 45 84

Method 1: We search for the maximum element k times in the given array. Each time we find one maximum element, we print it and replace it with minus infinite (Number.MIN_SAFE_INTEGER in Javascript) in the array. Also, the position of all k maximum elements is marked using an array so that with the help of that array we can print the elements in the order given in the original array. The time complexity of this method is O(n*k).

Javascript




<script>
 
// JavaScript program to find k maximum elements
// of array in original order
  
// Function to print k Maximum elements
function printMax(arr, k, n)
{
    var brr = Array(n).fill(0);
    var crr = Array(n)
     
      
    // Coping the array arr
    // into crr so that it
    // can be used later
    for(var i=0;i<n;i++)
    {
        crr[i]=arr[i];
    }
    // Iterating for K-times
    for(var i=0;i<k;i++)
    {
        // Finding the maximum element
        // along with its index
        var maxi=Number.MIN_SAFE_INTEGER;
        var index;
        for(var j=0;j<n;j++)
        {
            if(maxi<arr[j])
            {
                maxi=arr[j];
                index=j;
            }
        }
        // Assigning 1 in order
        // to mark the position
        // of all k maximum numbers
        brr[index]=1;
        arr[index]=Number.MIN_SAFE_INTEGER;
    }
      
    for(var i=0;i<n;i++)
    {
        // Printing the k maximum
        // elements array
        if(brr[i]==1)
        document.write(crr[i]+" ");
    }
}
 
// Driver code
var arr = [ 50, 8, 45, 12, 25, 40, 84 ];
var n = arr.length;
var k = 3;
printMax(arr, k, n);
 
// This code is contributed by Pushpesh raj
 
</script>

Time Complexity: O(n*k)
Auxiliary Space: O(n)

Method 2: In this method, we store the original array in a new array and will sort the new array in descending order. After sorting, we iterate the original array from 0 to n and print all those elements that appear in first k elements of new array. For searching, we can do Binary Search.

Javascript




<script>
 
// JavaScript program to find k maximum elements
// of array in original order
 
// Function to print m Maximum elements
function printMax(arr, k, n)
{
    // vector to store the copy of the
    // original array
    var brr = arr.slice();
 
    // Sorting the vector in descending
    // order. Please refer below link for
    // details
    brr.sort((a, b) => b - a);
     
    // Traversing through original array and
    // printing all those elements that are
    // in first k of sorted vector.
    // Please refer https://goo.gl/44Rwgt
    // for details of binary_search()
    for (var i = 0; i < n; ++i)
        if (brr.indexOf(arr[i]) < k)
            document.write(arr[i] +" ");
}
 
// Driver code
var arr = [ 50, 8, 45, 12, 25, 40, 84 ];
var n = arr.length;
var k = 3;
printMax(arr, k, n);
 
// This code is contributed by ShubhamSingh10
 
</script>

Output: 

50 45 84 

Time Complexity: O(n Log n) for sorting. 
Auxiliary Space: O(n)
 

Please refer complete article on Find k maximum elements of array in original order for more details!


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