LeetCode 1207. Unique Number of Occurrences

Description

https://leetcode.com/problems/unique-number-of-occurrences/

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

Explanation

Count occurences and check if numers of occurences having the same.

Python Solution

class Solution:
    def uniqueOccurrences(self, arr: List[int]) -> bool:
        visited = {}
        
        for num in arr:
            visited[num] = visited.get(num, 0) + 1
            
        
        values = set()
        for key, value in visited.items():
            if value in values:
                return False
            values.add(value)        
        
        return True
  • Time Complexity: O(N)
  • Space Complexity: O(N)

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