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Count the maximum number of elements that can be selected from the array
• Last Updated : 07 Jun, 2019

Given an array arr[], the task is to count the maximum number of elements that can be selected from the given array following the below selection process:

• At 1st selection, select an element which is greater than or equal to 1.
• At 2nd selection, select an element which is greater than or equal to 2.
• At 3rd selection, select an element which is greater than or equal to 3 and so on.

An element can be selected only once. The operation stops when it is not possible to select any element. So, the task is to maximize the count of selection from the array.

Examples:

Input : arr[] = { 4, 1, 3, 1 }
Output : 3
1st Selection: 1 is selected as 1 >= 1.
2nd Selection: 3 is selected as 3 >= 2.
3rd Selection: 4 is selected as 4 >= 3.
No more selections are possible. Therefore, the answers is 3.

Input : arr[] = { 2, 1, 1, 2, 1 }
Output : 2

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: In order to maximize the count of selection it is necessary to select the smallest possible numbers first and then the bigger numbers if the selection is not possible. This can be done easily by sorting the array. Now, loop through the array and increment the result by 1 when the element is greater than or equal to the number to select for the current operation.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;`` ` `// Function to return the maximum count of ``// selection possible from the given array ``// following the given process``int` `maxSelectionCount(``int` `a[], ``int` `n)``{``    ``// Initialize result``    ``int` `res = 0;`` ` `    ``// Sorting the array``    ``sort(a, a + n);`` ` `    ``// Initialize the select variable``    ``int` `select = 1;`` ` `    ``// Loop through array``    ``for` `(``int` `i = 0; i < n; i++) {``        ``// If selection is possible``        ``if` `(a[i] >= select) {``            ``res++; ``// Increment result``            ``select++; ``// Increment selection variable``        ``}``    ``}`` ` `    ``return` `res;``}`` ` `// Driver Code``int` `main()``{``    ``int` `arr[] = { 4, 2, 1, 3, 5, 1, 4 };`` ` `    ``int` `N = ``sizeof``(arr) / ``sizeof``(arr);`` ` `    ``cout << maxSelectionCount(arr, N);`` ` `    ``return` `0;``}`

## Java

 `// Java implementation of the approach``import` `java.util.*;`` ` `class` `GFG ``{`` ` `    ``// Function to return the maximum count of ``    ``// selection possible from the given array ``    ``// following the given process``    ``static` `int` `maxSelectionCount(``int` `a[], ``int` `n) ``    ``{``        ``// Initialize result``        ``int` `res = ``0``;`` ` `        ``// Sorting the array``        ``Arrays.sort(a);`` ` `        ``// Initialize the select variable``        ``int` `select = ``1``;`` ` `        ``// Loop through array``        ``for` `(``int` `i = ``0``; i < n; i++)``        ``{``            ``// If selection is possible``            ``if` `(a[i] >= select) ``            ``{``                ``res++; ``// Increment result``                ``select++; ``// Increment selection variable``            ``}``        ``}`` ` `        ``return` `res;``    ``}`` ` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``int` `arr[] = {``4``, ``2``, ``1``, ``3``, ``5``, ``1``, ``4``};`` ` `        ``int` `N = arr.length;`` ` `        ``System.out.println(maxSelectionCount(arr, N));``    ``}``}`` ` `// This code contributed by Rajput-Ji`

## Python3

 `# Python implementation of the approach`` ` `# Function to return the maximum count of ``# selection possible from the given array ``# following the given process``def` `maxSelectionCount(a, n):``    ``# Initialize result``    ``res ``=` `0``;`` ` `    ``# Sorting the array``    ``a.sort();`` ` `    ``# Initialize the select variable``    ``select ``=` `1``;`` ` `    ``# Loop through array``    ``for` `i ``in` `range``(n):``        ``# If selection is possible``        ``if` `(a[i] >``=` `select):``            ``res ``+``=` `1``; ``# Increment result``            ``select ``+``=` `1``; ``# Increment selection variable`` ` `    ``return` `res;`` ` ` ` `# Driver Code``arr ``=` `[ ``4``, ``2``, ``1``, ``3``, ``5``, ``1``, ``4` `];``N ``=` `len``(arr);``print``(maxSelectionCount(arr, N));`` ` `# This code contributed by PrinciRaj1992`

## C#

 `// C# implementation of the approach ``using` `System;`` ` `class` `GFG ``{ ``    ``// Function to return the maximum count of ``    ``// selection possible from the given array ``    ``// following the given process ``    ``static` `int` `maxSelectionCount(``int` `[]a, ``int` `n) ``    ``{ ``        ``// Initialize result ``        ``int` `res = 0; `` ` `        ``// Sorting the array ``        ``Array.Sort(a); `` ` `        ``// Initialize the select variable ``        ``int` `select` `= 1; `` ` `        ``// Loop through array ``        ``for` `(``int` `i = 0; i < n; i++) ``        ``{ ``            ``// If selection is possible ``            ``if` `(a[i] >= ``select``) ``            ``{ ``                ``res++; ``// Increment result ``                ``select``++; ``// Increment selection variable ``            ``} ``        ``} `` ` `        ``return` `res; ``    ``} `` ` `    ``// Driver Code ``    ``public` `static` `void` `Main() ``    ``{ ``        ``int` `[]arr = {4, 2, 1, 3, 5, 1, 4}; `` ` `        ``int` `N = arr.Length; `` ` `        ``Console.WriteLine(maxSelectionCount(arr, N)); ``    ``} ``} `` ` `// This code contributed by AnkitRai01`
Output:
```5
```

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