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 <= 1000 <= nums[i] <= 1000