# 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
```

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

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++ implementation of the approach ` `#include ` `using` `namespace` `std; ` `#define ll long long ` ` `  `ll ``int` `getCount(vector 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 v; ` `    ``v.push_back(1); ` `    ``v.push_back(2); ` `    ``v.push_back(3); ` `    ``v.push_back(4); ` ` `  `    ``cout << getCount(v, n); ` `    ``return` `0; ` `} `

 `// 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 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# 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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