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Tested Python solution for LeetCode 1394 with 27 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 1394 # by problem number
lcpy gen -s find_lucky_integer_in_an_array # by problem name
arr, a lucky integer is an integer that has a frequency in the array equal to its value.
Return the largest lucky integer in the array. If there is no lucky integer return -1.
Input: arr = [2,2,3,4]
Output: 2
Explanation: The only lucky number in the array is 2 because frequency[2] == 2.
Input: arr = [1,2,2,3,3,3]
Output: 3
Explanation: 1, 2 and 3 are all lucky numbers, return the largest of them.
Input: arr = [2,2,2,3,3]
Output: -1
Explanation: There are no lucky numbers in the array.
class Solution:
# Time: O(n)
# Space: O(n)
def find_lucky(self, arr: list[int]) -> int:
counts: dict[int, int] = {}
for value in arr:
counts[value] = counts.get(value, 0) + 1
result = -1
for value, count in counts.items():
if value == count:
result = max(result, value)
return result
| Time | Space |
|---|---|
| O(n) | O(n) |