public class Solution
extends Object
1394 - Find Lucky Integer in an Array\.
Easy
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`