Welcome to Subscribe On Youtube

Formatted question description: https://leetcode.ca/all/1207.html

1207. Unique Number of Occurrences (Easy)

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

Related Topics:
Hash Table

Solution 1.

• Java
• C++
• Python
• Go

• class Solution {
      public boolean uniqueOccurrences(int[] arr) {
          Map<Integer, Integer> map = new HashMap<Integer, Integer>();
          for (int num : arr) {
              int count = map.getOrDefault(num, 0);
              count++;
              map.put(num, count);
          }
          Set<Integer> set = new HashSet<Integer>();
          Set<Integer> keySet = map.keySet();
          for (int num : keySet) {
              int count = map.getOrDefault(num, 0);
              if (count != 0) {
                  if (!set.add(count))
                      return false;
              }
          }
          return true;
      }
  }
  
  ############
  
  class Solution {
      public boolean uniqueOccurrences(int[] arr) {
          Map<Integer, Integer> cnt = new HashMap<>();
          for (int x : arr) {
              cnt.merge(x, 1, Integer::sum);
          }
          return new HashSet<>(cnt.values()).size() == cnt.size();
      }
  }
  

• // OJ: https://leetcode.com/problems/unique-number-of-occurrences/
  // Time: O(N)
  // Space: O(N)
  class Solution {
  public:
      bool uniqueOccurrences(vector<int>& A) {
          unordered_map<int, int> m;
          for (int n : A) m[n]++;
          unordered_set<int> s;
          for (auto &p : m) {
              if (s.count(p.second)) return false;
              s.insert(p.second);
          }
          return true;
      }
  };
  

• class Solution:
      def uniqueOccurrences(self, arr: List[int]) -> bool:
          cnt = Counter(arr)
          return len(set(cnt.values())) == len(cnt)
  
  ############
  
  # 1207. Unique Number of Occurrences
  # https://leetcode.com/problems/unique-number-of-occurrences/
  
  class Solution:
      def uniqueOccurrences(self, arr: List[int]) -> bool:
          c = collections.Counter(arr)
          
          return len(set(c.values())) == len(c)
  
  

• func uniqueOccurrences(arr []int) bool {
  	cnt := map[int]int{}
  	for _, x := range arr {
  		cnt[x]++
  	}
  	vis := map[int]bool{}
  	for _, v := range cnt {
  		if vis[v] {
  			return false
  		}
  		vis[v] = true
  	}
  	return true
  }
  

All Problems

All Solutions