# [Solved] 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.

## Question

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`

## Python Solution

```class Solution:
def findLucky(self, arr: List[int]) -> int:
arr.sort(reverse=True)
d = collections.Counter(arr)
for k,v in d.items():
if k==v:
return k
return -1```