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Tested Python solution for LeetCode 1608 with 18 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 1608 # by problem number
lcpy gen -s special_array_with_x_elements_greater_than_or_equal_x # by problem name
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.
Input: nums = [3,5]
Output: 2
Explanation: There are 2 values (3 and 5) that are greater than or equal to 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.
Input: nums = [0,4,3,0,4]
Output: 3
Explanation: There are 3 values that are greater than or equal to 3.
1 <= nums.length <= 1000 <= nums[i] <= 1000class Solution:
# Time: O(n + m) where m = max(nums)
# Space: O(m)
def special_array(self, nums: list[int]) -> int:
n = len(nums)
counts = [0] * (n + 1)
for num in nums:
counts[min(num, n)] += 1
total = 0
for x in range(n, -1, -1):
total += counts[x]
if total == x:
return x
return -1
| Time | Space |
|---|---|
| O(n + m) where m = max(nums) | O(m) |