【leetcode】1207. Unique Number of Occurrences

题目如下：

Given an array of integers arr, write a function that returns true if and only if the number of occurrences of each value in the array is unique.

Example 1:

Input: arr = [1,2,2,1,1,3]
Output: true
Explanation: The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences.

Example 2:

Input: arr = [1,2]
Output: false

Example 3:

Input: arr = [-3,0,1,-3,1,1,1,-3,10,0]
Output: true

Constraints:

• 1 <= arr.length <= 1000
• -1000 <= arr[i] <= 1000

解题思路：很简单的题目。

代码如下：

class Solution(object):
    def uniqueOccurrences(self, arr):
        """
        :type arr: List[int]
        :rtype: bool
        """
        dic = {}
        for i in arr:
            dic[i] = dic.setdefault(i,0) + 1
        dic_exist = {}
        for v in dic.itervalues():
            if v in dic_exist:
                return False
            dic_exist[v] = 1
        return True