LeetCode #1394. Find Lucky Integer in an Array

题目

1394. Find Lucky Integer in an Array

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解题方法

遍历数组计算每个数字的频率，存入字典，设置返回值rat=-1并遍历字典中的键，如果key - dic[key] == 0，则设置rat = max(rat, key)，最后返回rat。
时间复杂度：O(n)
空间复杂度：O(n)

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代码

class Solution:
    def findLucky(self, arr: List[int]) -> int:
        dic = {}
        for i in arr:
            if i not in dic:
                dic[i] = 1
            else:
                dic[i] += 1
        
        rat = -1
        for key in dic.keys():
            if not key - dic[key]:
                rat = max(rat, key)
        
        return rat