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1394. Find Lucky Integer in an Array

Difficulty Topics

Description

Given an array of integers 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.

 

Example 1:

Input: arr = [2,2,3,4]
Output: 2
Explanation: The only lucky number in the array is 2 because frequency[2] == 2.

Example 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.

Example 3:

Input: arr = [2,2,2,3,3]
Output: -1
Explanation: There are no lucky numbers in the array.

 

Constraints:

  • 1 <= arr.length <= 500
  • 1 <= arr[i] <= 500

Solution

find-lucky-integer-in-an-array.py
class Solution:
    def findLucky(self, arr: List[int]) -> int:

        C = collections.Counter(arr)
        res = -1
        for c in C:
            if c == C[c]:
                res = max(res, c)

        return res