1207. Unique Number of Occurrences

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1. 紀錄各 num 出現頻率
2. 判斷唯一性

class Solution:
    def uniqueOccurrences(self, arr: List[int]) -> bool:
        freq_map, occur_set = {}, set()
        for num in arr:
            freq_map[num] = freq_map.get(num, 0) + 1
        for freq in freq_map.values():
            if freq in occur_set:
                return False
            occur_set.add(freq)
        return True

[fockspaces]

improve: 直接用 set 建構來判斷是否有重複元素

class Solution:
    def uniqueOccurrences(self, arr: List[int]) -> bool:
        freq_map, occur_set = {}, set()
        for num in arr:
            freq_map[num] = freq_map.get(num, 0) + 1
        occur_set = set(freq_map.values())
        return len(occur_set) == len(freq_map.values())