Today I have done leetcode's May LeetCoding Challenge with cpp.

May LeetCoding Challenge 27

Description

Special Array With X Elements Greater Than or Equal X

You are given an array nums of non-negative integers. nums is considered special if there exists a number x such that there are exactly x numbers in nums that are greater than or equal to x.

Notice that x does not have to be an element in nums.

Return x if the array is special, otherwise, return -1. It can be proven that if nums is special, the value for x is unique.

Example 1:

Input: nums = [3,5]
Output: 2
Explanation: There are 2 values (3 and 5) that are greater than or equal to 2.

Example 2:

Input: nums = [0,0]
Output: -1
Explanation: No numbers fit the criteria for x.
If x = 0, there should be 0 numbers >= x, but there are 2.
If x = 1, there should be 1 number >= x, but there are 0.
If x = 2, there should be 2 numbers >= x, but there are 0.
x cannot be greater since there are only 2 numbers in nums.

Example 3:

Input: nums = [0,4,3,0,4]
Output: 3
Explanation: There are 3 values that are greater than or equal to 3.

Constraints:

• 1 <= nums.length <= 100
• 0 <= nums[i] <= 1000

Solution

class Solution {
public:
  int specialArray(vector<int>& nums) {
    sort(nums.begin(), nums.end(), greater<int>());
    for(int i = 0; i < nums.size(); ++i) {
      if(nums[i] >= i + 1 && (i + 1 >= nums.size() || nums[i + 1] < i + 1)) return i + 1;
    }
    return -1;
  }
};