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++ 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. |
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++ 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
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!