1207. Unique Number of Occurrences
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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
class Solution public boolean uniqueOccurrences(int[] arr) Arrays.sort(arr); HashMap<Integer, Integer> map = new HashMap(); for(int i: arr) map.put(i, 1 + map.getOrDefault(i, 0)); ArrayList<Integer> list = new ArrayList(map.values()); Collections.sort(list); for(int i = 1; i < list.size(); i++) if(list.get(i) == list.get(i-1)) return false; return true;
绕远路还是我会绕。
HashMap的values() 方法返回一个values的set,形式为collections,所以可以转化为list
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