Find Lucky Integer in an Array
Easy
You receive an array of integers arr, a lucky integer is an integer that has a frequency in the array equal to its value.
Find and provide the largest lucky integer in the array. If there is no lucky integer provide -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, provide 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 <= 5001 <= arr[i] <= 500
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