C++ Program to Find k maximum elements of array in original order

Last Updated : 17 Aug, 2023

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 (INT_MIN in C) in the array. The time complexity of this method is O(n*k).

C++

// C++ program to find k Maximum elements #include <bits/stdc++.h> using namespace std;  // Function to print k Maximum elements void printMax(int a[], int n, int k) {     int b[n],c[n];          // Coping the array a     // into c and initialising     // elements in array b as 0.     for(int i=0;i<n;i++)     {         c[i]=a[i];         b[i]=0;     }          // Iterating for K-times     // to find k-maximum     for(int i=0;i<k;i++)     {         // finding the maximum element         // and its index         int maxi=INT_MIN;         int index;         for(int j=0;j<n;j++)         {             if(a[j]>maxi)             {                 maxi=a[j];                 index=j;             }         }         // Assigning 1 in order         // to mark the position         // of all k maximum numbers         b[index]=1;         a[index]=INT_MIN;     }          for(int i=0;i<n;i++)     {         // Printing the k maximum         // elements of the array         if(b[i]==1)         cout<<c[i]<<" ";     } }  // Driver code int main() {     int a[] = { 50, 8, 45, 12, 25, 40, 84 };     int n = sizeof(a) / sizeof(a[0]);     int k = 3;     printMax(a, n, k);     return 0; }  // This code is contributed by Aman kumar.

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.

C++

// C++ program to find k maximum elements  // of array in original order #include <bits/stdc++.h> using namespace std;  // Function to print m Maximum elements void printMax(int arr[], int k, int n) {     // vector to store the copy of the     // original array     vector<int> brr(arr, arr + n);      // Sorting the vector in descending     // order. Please refer below link for     // details     // https://www.geeksforgeeks.org/sort-c-stl/     sort(brr.begin(), brr.end(), greater<int>());      // 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 (int i = 0; i < n; ++i)         if (binary_search(brr.begin(),                  brr.begin() + k, arr[i],                          greater<int>()))             cout << arr[i] << " "; }  // Driver code int main() {     int arr[] = { 50, 8, 45, 12, 25, 40, 84 };     int n = sizeof(arr) / sizeof(arr[0]);     int k = 3;     printMax(arr, k, n);     return 0; }

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!

C++ Program to Find Largest Element in an Array

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C++ Program to Find k maximum elements of array in original order

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