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.
// 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;
}
};
Java
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;
}
}