Unique Number of Occurrences

Description

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

Solution(javascript)

/*
 * @lc app=leetcode id=1207 lang=javascript
 *
 * [1207] Unique Number of Occurrences
 */

// @lc code=start
/**
 * @param {number[]} arr
 * @return {boolean}
 */
const uniqueOccurrences = function (arr) {
  const countMap = arr.reduce((acc, num) => {
    acc[num] = (acc[num] || 0) + 1
    return acc
  }, {})
  const values = Object.values(countMap)
  const set = new Set(values)

  return values.length === set.size
}
// @lc code=end