1608. Special Array With X Elements Greater Than or Equal X.py

'''
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
'''

class Solution:
    def specialArray(self, nums):
        nums.sort()
        dc = dict()
        for i in range(len(nums)):
            if nums[i] not in dc:
                dc[nums[i]] = i
        for i in range(len(nums)):
            v = nums[i]
            e = len(nums)-i
            if e<=v:
                if e == len(nums):
                    return e
                else:
                    if nums[i-1]<e<=nums[i]:
                        return e

        return -1