Count elements such that there are exactly X elements with values greater than or equal to X

Given an array *arr* of *N* integers, the task is to find the number of elements that satisfy the following condition:

If the element is *X* then there has to be exactly *X* number of elements in the array (excluding the number *X*) which are greater than or equal to *X*

**Examples:**

Input:arr[] = {1, 2, 3, 4}Output:1 Only element 2 satisfies the condition as there are exactly 2 elements which are greater than or equal to 2 (3, 4) except 2 itself.Input:arr[] = {5, 5, 5, 5, 5}Output:0

**Approach:** The problem involves efficient searching for each arr[i] element the number of arr[j]’s (i != j) which are greater than or equal to arr[i].

- Sort the array in ascending order.
- For every element arr[i], using binary search get the count of all the elements that are greater than or equal to arr[i] except arr[i] itself.
- If the count is equal to arr[i] then increment the result.
- Print the value of the result in the end.

Below is the implementation of the above approach:

## C++

`// C++ implementation of the approach` `#include <bits/stdc++.h>` `using` `namespace` `std;` `#define ll long long` ` ` `ll ` `int` `getCount(vector<ll ` `int` `> v, ` `int` `n)` `{` ` ` `// Sorting the vector` ` ` `sort((v).begin(), (v).end());` ` ` `ll ` `int` `cnt = 0;` ` ` `for` `(ll ` `int` `i = 0; i < n; i++) {` ` ` ` ` `// Count of numbers which` ` ` `// are greater than v[i]` ` ` `ll ` `int` `tmp = v.end() - 1` ` ` `- upper_bound((v).begin(), (v).end(), v[i] - 1);` ` ` ` ` `if` `(tmp == v[i])` ` ` `cnt++;` ` ` `}` ` ` `return` `cnt;` `}` ` ` `// Driver code` `int` `main()` `{` ` ` `ll ` `int` `n;` ` ` `n = 4;` ` ` `vector<ll ` `int` `> v;` ` ` `v.push_back(1);` ` ` `v.push_back(2);` ` ` `v.push_back(3);` ` ` `v.push_back(4);` ` ` ` ` `cout << getCount(v, n);` ` ` `return` `0;` `}` |

## Java

`// Java implementation of the approach` `import` `java.util.*;` ` ` `class` `GFG ` `{` ` ` `static` `int` `getCount(` `int` `[] v, ` `int` `n)` ` ` `{` ` ` ` ` `// Sorting the vector` ` ` `Arrays.sort(v);` ` ` `int` `cnt = ` `0` `;` ` ` `for` `(` `int` `i = ` `0` `; i < n; i++) ` ` ` `{` ` ` ` ` `// Count of numbers which` ` ` `// are greater than v[i]` ` ` `int` `tmp = n - ` `1` `- upperBound(v, n, v[i] - ` `1` `);` ` ` `if` `(tmp == v[i])` ` ` `cnt++;` ` ` `}` ` ` `return` `cnt;` ` ` `}` ` ` ` ` `// Function to implement upper_bound()` ` ` `static` `int` `upperBound(` `int` `[] array, ` ` ` `int` `length, ` `int` `value) ` ` ` `{` ` ` `int` `low = ` `0` `;` ` ` `int` `high = length;` ` ` `while` `(low < high) ` ` ` `{` ` ` `final` `int` `mid = (low + high) / ` `2` `;` ` ` `if` `(value >= array[mid]) ` ` ` `{` ` ` `low = mid + ` `1` `;` ` ` `} ` ` ` `else` ` ` `{` ` ` `high = mid;` ` ` `}` ` ` `}` ` ` `return` `low;` ` ` `}` ` ` ` ` `// Driver Code` ` ` `public` `static` `void` `main(String[] args) ` ` ` `{` ` ` `int` `n = ` `4` `;` ` ` `int` `[] v = { ` `1` `, ` `2` `, ` `3` `, ` `4` `};` ` ` `System.out.println(getCount(v, n));` ` ` `}` `}` ` ` `// This code is contributed by` `// sanjeev2552` |

## Python3

`# Python3 implementation of the approach` `from` `bisect ` `import` `bisect as upper_bound` ` ` `def` `getCount(v, n):` ` ` ` ` `# Sorting the vector` ` ` `v ` `=` `sorted` `(v)` ` ` `cnt ` `=` `0` ` ` `for` `i ` `in` `range` `(n):` ` ` ` ` `# Count of numbers which` ` ` `# are greater than v[i]` ` ` `tmp ` `=` `n ` `-` `1` `-` `upper_bound(v, v[i] ` `-` `1` `)` ` ` ` ` `if` `(tmp ` `=` `=` `v[i]):` ` ` `cnt ` `+` `=` `1` ` ` `return` `cnt` ` ` `# Driver codemain()` `n ` `=` `4` `v ` `=` `[]` `v.append(` `1` `)` `v.append(` `2` `)` `v.append(` `3` `)` `v.append(` `4` `)` ` ` `print` `(getCount(v, n))` ` ` `# This code is contributed by Mohit Kumar` |

## C#

`// C# implementation of the approach` `using` `System;` ` ` `class` `GFG ` `{` ` ` `static` `int` `getCount(` `int` `[] v, ` `int` `n)` ` ` `{` ` ` ` ` `// Sorting the vector` ` ` `Array.Sort(v);` ` ` `int` `cnt = 0;` ` ` `for` `(` `int` `i = 0; i < n; i++) ` ` ` `{` ` ` ` ` `// Count of numbers which` ` ` `// are greater than v[i]` ` ` `int` `tmp = n - 1 - upperBound(v, n, v[i] - 1);` ` ` `if` `(tmp == v[i])` ` ` `cnt++;` ` ` `}` ` ` `return` `cnt;` ` ` `}` ` ` ` ` `// Function to implement upper_bound()` ` ` `static` `int` `upperBound(` `int` `[] array, ` ` ` `int` `length, ` `int` `value) ` ` ` `{` ` ` `int` `low = 0;` ` ` `int` `high = length;` ` ` `while` `(low < high) ` ` ` `{` ` ` `int` `mid = (low + high) / 2;` ` ` `if` `(value >= array[mid]) ` ` ` `{` ` ` `low = mid + 1;` ` ` `} ` ` ` `else` ` ` `{` ` ` `high = mid;` ` ` `}` ` ` `}` ` ` `return` `low;` ` ` `}` ` ` ` ` `// Driver Code` ` ` `public` `static` `void` `Main(String[] args) ` ` ` `{` ` ` `int` `n = 4;` ` ` `int` `[] v = { 1, 2, 3, 4 };` ` ` `Console.WriteLine(getCount(v, n));` ` ` `}` `}` ` ` `// This code is contributed by PrinciRaj1992` |

**Output:**

1

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