1207. Unique Number of Occurrences (Python3)
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
IDEAS：
- 想到數字出現的次數，我們首先會聯想到字典(dict)，首先定義字典d去統計每個數字出現的次數
- 判斷每個數字出現的次數是否有重複，也會聯想到Python裏面判斷元素是否有重的一個小技巧：
len(set(list) == len(list)
class Solution:
def uniqueOccurrences(self, arr: List[int]) -> bool:
res=[]
d={item:{'occurrence':0} for item in arr} # dict
for c in arr:
d[c]['occurrence']+=1
for c in d:
res.append(d[c]['occurrence'])
return len(set(res)) == len(res)