Related Articles

# Minimum number of operations required to delete all elements of the array

• Difficulty Level : Easy
• Last Updated : 30 Apr, 2021

Given an integer array arr, the task is to print the minimum number of operations required to delete all elements of the array.
In an operation, any element from the array can be chosen at random and every element divisible by it can be removed from the array.
Examples:

Input: arr[] = {2, 4, 6, 3, 5, 10}
Output:
Choosing 2 as the first element will remove 2, 4, 6 and 10 from the array.
Now choose 3 which will result in the removal of 3.
Finally, the only element left to choose is 5.
Input: arr[] = {2, 5, 3, 7, 11}
Output:

Approach: For optimal results, the smallest element from the array should be chosen from the remaining elements one after another until all the elements of the array are deleted.

• Sort the array in ascending order and prepare a hash for occurrences.
• For each unmarked element starting from beginning mark all elements which are divisible by choose element, and increase the result counter.

Below is the implementstion of the above approach

## C++

 `// C++ implementation of the above approach` `#include ``#define MAX 10000` `using` `namespace` `std;` `int` `hashTable[MAX];` `// function to find minimum operations``int` `minOperations(``int` `arr[], ``int` `n)``{``    ``// sort array``    ``sort(arr, arr + n);` `    ``// prepare hash of array``    ``for` `(``int` `i = 0; i < n; i++)``        ``hashTable[arr[i]]++;` `    ``int` `res = 0;``    ``for` `(``int` `i = 0; i < n; i++) {``        ``if` `(hashTable[arr[i]]) {``            ``for` `(``int` `j = i; j < n; j++)``                ``if` `(arr[j] % arr[i] == 0)``                    ``hashTable[arr[j]] = 0;``            ``res++;``        ``}``    ``}` `    ``return` `res;``}` `// Driver program``int` `main()``{``    ``int` `arr[] = { 4, 6, 2, 8, 7, 21, 24, 49, 44 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);` `    ``cout << minOperations(arr, n);``    ``return` `0;``}`

## Java

 `//Java implementation of the above approach``import` `java.util.*;``class` `Solution``{``static` `final` `int` `MAX=``10000``;` `static` `int` `hashTable[]= ``new` `int``[MAX];` `// function to find minimum operations``static` `int` `minOperations(``int` `arr[], ``int` `n)``{``    ``// sort array``    ``Arrays.sort(arr);` `    ``// prepare hash of array``    ``for` `(``int` `i = ``0``; i < n; i++)``        ``hashTable[arr[i]]++;` `    ``int` `res = ``0``;``    ``for` `(``int` `i = ``0``; i < n; i++) {``        ``if` `(hashTable[arr[i]]!=``0``) {``            ``for` `(``int` `j = i; j < n; j++)``                ``if` `(arr[j] % arr[i] == ``0``)``                    ``hashTable[arr[j]] = ``0``;``            ``res++;``        ``}``    ``}` `    ``return` `res;``}` `// Driver program``public` `static` `void` `main(String args[])``{``    ``int` `arr[] = { ``4``, ``6``, ``2``, ``8``, ``7``, ``21``, ``24``, ``49``, ``44` `};``    ``int` `n = arr.length;` `    ``System.out.print( minOperations(arr, n));`` ` `}``}``// This code is contributed by Arnab Kundu`

## Python 3

 `# Python 3 implementation of``# the above approach``MAX` `=` `10000` `hashTable ``=` `[``0``] ``*` `MAX` `# function to find minimum operations``def` `minOperations(arr, n):``    ` `    ``# sort array``    ``arr.sort()` `    ``# prepare hash of array``    ``for` `i ``in` `range``(n):``        ``hashTable[arr[i]] ``+``=` `1` `    ``res ``=` `0``    ``for` `i ``in` `range``(n) :``        ``if` `(hashTable[arr[i]]) :``            ``for` `j ``in` `range``(i, n):``                ``if` `(arr[j] ``%` `arr[i] ``=``=` `0``):``                    ``hashTable[arr[j]] ``=` `0``            ``res ``+``=` `1` `    ``return` `res` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:``    ``arr ``=` `[ ``4``, ``6``, ``2``, ``8``, ``7``, ``21``, ``24``, ``49``, ``44` `]``    ``n ``=` `len``(arr)` `    ``print``(minOperations(arr, n))` `# This code is contributed``# by ChitraNayal`

## C#

 `using` `System;` `// C# implementation of the above approach ``public` `class` `Solution``{``public` `const` `int` `MAX = 10000;` `public` `static` `int``[] hashTable = ``new` `int``[MAX];` `// function to find minimum operations ``public` `static` `int` `minOperations(``int``[] arr, ``int` `n)``{``    ``// sort array ``    ``Array.Sort(arr);` `    ``// prepare hash of array ``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``hashTable[arr[i]]++;``    ``}` `    ``int` `res = 0;``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``if` `(hashTable[arr[i]] != 0)``        ``{``            ``for` `(``int` `j = i; j < n; j++)``            ``{``                ``if` `(arr[j] % arr[i] == 0)``                ``{``                    ``hashTable[arr[j]] = 0;``                ``}``            ``}``            ``res++;``        ``}``    ``}` `    ``return` `res;``}` `// Driver program ``public` `static` `void` `Main(``string``[] args)``{``    ``int``[] arr = ``new` `int``[] {4, 6, 2, 8, 7, 21, 24, 49, 44};``    ``int` `n = arr.Length;` `    ``Console.Write(minOperations(arr, n));` `}``}` `// This code is contributed by Shrikant13`

## PHP

 ``

## Javascript

 ``
Output:
`2`

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

My Personal Notes arrow_drop_up