text: # [1207. Unique Number of Occurrences](https://leetcode.com/problems/unique-number-of-occurrences/)
  
  
  ## 题目
  
  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`
  
  
  
  ## 题目大意
  
  给你一个整数数组 arr，请你帮忙统计数组中每个数的出现次数。如果每个数的出现次数都是独一无二的，就返回 true；否则返回 false。
  
  提示：
  
  - 1 <= arr.length <= 1000
  - -1000 <= arr[i] <= 1000
  
  ## 解题思路
  
  
  - 给出一个数组，先统计每个数字出现的频次，判断在这个数组中是否存在相同的频次。
  - 简单题，先统计数组中每个数字的频次，然后用一个 map 判断频次是否重复。
  