https://leetcode.com/problems/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.

Example 4:

Input: nums = [3,6,7,7,0]

Output: -1

Constraints:

1 <= nums.length <= 100

0 <= nums[i] <= 1000

1 | class Solution { |