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: HashTable
Time complexity: O(n)
Space complexity: O(n)
C++
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// Author: Huahua class Solution { public: bool uniqueOccurrences(vector<int>& arr) { unordered_map<int, int> c; for (int a : arr) ++c[a]; unordered_set<int> s; for (const auto& kv : c) if (!s.insert(kv.second).second) return false; return true; } }; |
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