1207. Unique Number of Occurrences LeetCode Solution

In this guide, you will get 1207. Unique Number of Occurrences LeetCode Solution with the best time and space complexity. The solution to Unique Number of Occurrences problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.

Problem Statement
Complexity Analysis
Unique Number of Occurrences solution in C++
Unique Number of Occurrences solution in Java
Unique Number of Occurrences solution in Python
Additional Resources

1207. Unique Number of Occurrences LeetCode Solution image

Problem Statement of Unique Number of Occurrences

Given an array of integers arr, return true if the number of occurrences of each value in the array is unique or false otherwise.

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

Complexity Analysis

Time Complexity: O(n)
Space Complexity: O(n)

1207. Unique Number of Occurrences LeetCode Solution in C++

class Solution {
 public:
  bool uniqueOccurrences(vector<int>& arr) {
    unordered_map<int, int> count;
    unordered_set<int> occurrences;

    for (const int a : arr)
      ++count[a];

    for (const auto& [_, value] : count)
      if (!occurrences.insert(value).second)
        return false;

    return true;
  }
};
/* code provided by PROGIEZ */

1207. Unique Number of Occurrences LeetCode Solution in Java

class Solution {
  public boolean uniqueOccurrences(int[] arr) {
    Map<Integer, Integer> count = new HashMap<>();
    Set<Integer> occurrences = new HashSet<>();

    for (final int a : arr)
      count.merge(a, 1, Integer::sum);

    for (final int value : count.values())
      if (!occurrences.add(value))
        return false;

    return true;
  }
}
// code provided by PROGIEZ

1207. Unique Number of Occurrences LeetCode Solution in Python

class Solution:
  def uniqueOccurrences(self, arr: list[int]) -> bool:
    count = collections.Counter(arr)
    occurrences = set()

    for value in count.values():
      if value in occurrences:
        return False
      occurrences.add(value)

    return True
 # code by PROGIEZ