Related Articles

# Find the index of the element in an array which divides most elements before it

• Difficulty Level : Easy
• Last Updated : 25 May, 2021

Given an array arr, the task is to find the index of the element in an array which divides most elements before it
Examples:

```Input: arr = {5, 2, 1, 4, 5, 8, 2}
Output: 6
Explanation
arr[6] = 2
it divides 2, 4, and 8 (3 elements)

Input: arr = {8, 1, 28, 4, 1, 6, 7}
Output: 4```

Approach:

• Maintain a map.
• For each arr[i] update the count variable by looking into map for ar[i] and insert all divisor of ar[i] into map.
• Update maxElement if cnt > maxx.
• Finally return the index with maxElement.

Below is the implementation of above approach:

## CPP

 `// C++ program find the index of the element``// in an array which divides``// most elements before it` `#include ``using` `namespace` `std;` `// Function to get the max element``// divisible by arr[i]``int` `maxElement(``int` `arr[], ``int` `n)``{` `    ``map<``int``, ``int``> mp;``    ``int` `maxx = -1, maxElement = -1;` `    ``for` `(``int` `i = 0; i < n; i++) {``        ``int` `num = arr[i];``        ``int` `cnt = 0;` `        ``// Update count for A[i]``        ``if` `(mp.find(num) != mp.end()) {``            ``cnt += mp[num];``        ``}` `        ``// Generate Divisor For A[i]``        ``for` `(``int` `j = 1; j * j <= num; j++) {``            ``if` `(num % j == 0) {``                ``mp[j]++;``                ``if` `(j != num / j)``                    ``mp[num / j]++;``            ``}``        ``}` `        ``// Update Max Element``        ``if` `(cnt > maxx) {``            ``maxElement = i;``            ``maxx = cnt;``        ``}``    ``}` `    ``return` `maxElement;``}` `// Driver code``int` `main()``{` `    ``int` `arr[] = { 5, 2, 1, 4, 5, 8, 2 };``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr[0]);` `    ``cout << maxElement(arr, n) << ``'\n'``;` `    ``return` `0;``}`

## Java

 `// Java program find the index of the element``// in an array which divides``// most elements before it``import` `java.util.*;` `class` `GFG``{` `    ``// Function to get the max element``    ``// divisible by arr[i]``    ``static` `int` `maxElement(``int` `arr[], ``int` `n)``    ``{` `        ``HashMap mp = ``new` `HashMap();``        ``int` `maxx = -``1``, maxElement = -``1``;` `        ``for` `(``int` `i = ``0``; i < n; i++)``        ``{``            ``int` `num = arr[i];``            ``int` `cnt = ``0``;` `            ``// Update count for A[i]``            ``if` `(mp.containsKey(num))``            ``{``                ``cnt += mp.get(num);``            ``}` `            ``// Generate Divisor For A[i]``            ``for` `(``int` `j = ``1``; j * j <= num; j++)``            ``{``                ``if` `(num % j == ``0``)``                ``{``                    ``if` `(mp.containsKey(j))``                        ``mp.put(j, mp.get(j) + ``1``);``                    ``else``                        ``mp.put(j, ``1``);``                    ``if` `(j != num / j)``                        ``if` `(mp.containsKey(num / j))``                            ``mp.put(num / j, mp.get(num / j) + ``1``);``                        ``else``                            ``mp.put(num / j, ``1``);``                ``}``            ``}` `            ``// Update Max Element``            ``if` `(cnt > maxx)``            ``{``                ``maxElement = i;``                ``maxx = cnt;``            ``}``        ``}` `        ``return` `maxElement;``    ``}` `    ``// Driver code``    ``public` `static` `void` `main(String[] args)``    ``{` `        ``int` `arr[] = { ``5``, ``2``, ``1``, ``4``, ``5``, ``8``, ``2` `};``        ``int` `n = arr.length;` `        ``System.out.print(maxElement(arr, n));``    ``}``}` `// This code is contributed by 29AjayKumar`

## Python

 `# Python3 program find the index of the element``# in an array which divides``# most elements before it` `# Function to get the max element``# divisible by arr[i]``def` `maxElement(arr, n):` `    ``mp ``=` `dict``()``    ``maxx ``=` `-``1``    ``maxElement ``=` `-``1` `    ``for` `i ``in` `range``(n):``        ``num ``=` `arr[i]``        ``cnt ``=` `0` `        ``# Update count for A[i]``        ``if` `(num ``in` `mp):``            ``cnt ``+``=` `mp[num]` `        ``# Generate Divisor For A[i]``        ``j ``=` `1` `        ``while` `j ``*` `j <``=` `num:``            ``if` `(num ``%` `j ``=``=` `0``):``                ``mp[j] ``=` `mp.get(j, ``0``) ``+` `1``                ``if` `(j !``=` `num ``/``/` `j):``                    ``mp[num ``/``/` `j] ``=` `mp.get(num``/``/``j, ``0``) ``+` `1``            ``j ``+``=` `1` `        ``# Update Max Element``        ``if` `(cnt > maxx):``            ``maxElement ``=` `i``            ``maxx ``=` `cnt` `    ``return` `maxElement` `# Driver code``arr ``=` `[``5``, ``2``, ``1``, ``4``, ``5``, ``8``, ``2``]``n ``=` `len``(arr)` `print``(maxElement(arr, n))` `# This code is contributed by mohit kumar 29`

## C#

 `// C# program find the index of the element``// in an array which divides``// most elements before it``using` `System;``using` `System.Collections.Generic;` `class` `GFG``{` `    ``// Function to get the max element``    ``// divisible by arr[i]``    ``static` `int` `maxElement(``int` `[]arr, ``int` `n)``    ``{` `        ``Dictionary<``int``, ``int``> mp = ``new` `Dictionary<``int``, ``int``>();``        ``int` `maxx = -1, maxElement = -1;` `        ``for` `(``int` `i = 0; i < n; i++)``        ``{``            ``int` `num = arr[i];``            ``int` `cnt = 0;` `            ``// Update count for A[i]``            ``if` `(mp.ContainsKey(num))``            ``{``                ``cnt += mp[num];``            ``}` `            ``// Generate Divisor For A[i]``            ``for` `(``int` `j = 1; j * j <= num; j++)``            ``{``                ``if` `(num % j == 0)``                ``{``                    ``if` `(mp.ContainsKey(j))``                        ``mp[j] = mp[j] + 1;``                    ``else``                        ``mp.Add(j, 1);``                    ``if` `(j != num / j)``                        ``if` `(mp.ContainsKey(num / j))``                            ``mp[num / j] = mp[num / j] + 1;``                        ``else``                            ``mp.Add(num / j, 1);``                ``}``            ``}` `            ``// Update Max Element``            ``if` `(cnt > maxx)``            ``{``                ``maxElement = i;``                ``maxx = cnt;``            ``}``        ``}` `        ``return` `maxElement;``    ``}` `    ``// Driver code``    ``public` `static` `void` `Main(String[] args)``    ``{` `        ``int` `[]arr = { 5, 2, 1, 4, 5, 8, 2 };``        ``int` `n = arr.Length;` `        ``Console.Write(maxElement(arr, n));``    ``}``}` `// This code is contributed by PrinciRaj1992`

## Javascript

 ``
Output:

`6`

Time Complexity: O(N√max(Arr))

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