leetcode1394

class Solution:
    def findLucky(self, arr: List[int]) -> int:
        dic = dict()
        n = len(arr)
        for i in range(n):
            if arr[i] not in dic:
                dic[arr[i]] = 1
            else:
                dic[arr[i]] += 1
        maxnum = -1 
        for k,v in dic.items():
            if k == v and v > maxnum:
                maxnum = v
        return maxnum

算法思路：hash