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

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 (-1*sys.maxsize for largest minimum value in Python) 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). 

Python3

# Python program to find k maximum elements
# of array in original order

# import the module
import sys

# Function to print k Maximum elements
def printMax(arr, k, n):
    brr=[0]*n
    crr=[0]*n

    # Coping the array arr
    # into crr so that it
    # can be used later
    for i in range(n):
        crr[i]=arr[i]

    # Iterating for K-times
    for i in range(k):
        # Finding the maximum element
        # along with its index
        maxi=-1*sys.maxsize
        for j in range(n):
            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]=-1*sys.maxsize

    for i in range(n):
        # Printing the k maximum
        # elements array
        if(brr[i]==1):
            print(crr[i],end=" ")



# Driver code
arr = [ 50, 8, 45, 12, 25, 40, 84 ]
n = len(arr)
k = 3;
printMax(arr, k, n)

# This code is contributed by Pushpesh Raj.

Output

50 45 84 

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.

Python3

# Python3 program to find k maximum elements
# of array in original order

# Function to print  Maximum elements
def printMax(arr, k, n):

    # vector to store the copy of the
    # original array
    brr = arr.copy()

    # Sorting the vector in descending
    # order. Please refer below link for
    # details
    brr.sort(reverse = True)

    # Traversing through original array and
    # print all those elements that are
    # in first k of sorted vector.
    for i in range(n):
        if (arr[i] in brr[0:k]):
            print(arr[i], end = " ")

# Driver code
arr = [ 50, 8, 45, 12, 25, 40, 84 ]
n = len(arr)
k = 3

printMax(arr, k, n)

# This code is contributed by SHUBHAMSINGH10

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!