솜씨좋은장씨

Given an array of integers arr, a lucky integer is an integer which has a frequency in the array equal to its value. Return a lucky integer in the array. If there are multiple lucky integers return the largest of them. 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: Inpu..