Added Leetcode Solution 1207

dsa-solutions/lc-solutions/1200-1299/1207-unique-number-of-occurrences.md

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+---
+id: unique-number-of-occurrences
+title: Unique Number of Occurrences
+sidebar_label: 1207. Unique Number of Occurrences
+tags:
+- Array
+- Hash Table
+description: "Solution to Leetcode 1207. Unique Number of Occurrences"
+---
+
+## Problem Description
+
+Given an array of integers arr, return true if the number of occurrences of each value in the array is unique or false otherwise.
+
+### Examples
+
+**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
+```
+
+
+
+### Constraints
+- `1 <= arr.length <= 1000`
+- `-1000 <= arr[i] <= 1000`
+
+### Approach 
+1. Sort the input array arr to group identical elements together.
+2. Traverse the sorted array, counting occurrences of each element.
+3. Store the counts in a separate vector v.
+4. Sort the vector v to make it easier to check for duplicates.
+5. Iterate through v and check if adjacent elements are equal. If so, return false.
+6. If the loop completes, it means all counts are unique, and the function returns true.
+
+### Complexity
+
+Time complexity: $O(n)$
+Space complexity: $O(n)$
+
+### Solution
+
+#### Code in Different Languages
+
+#### C++
+
+ ```cpp
+class Solution {
+public:
+    bool uniqueOccurrences(vector<int>& arr) {
+      unordered_map<int,int>freq;
+      for(auto x: arr){
+          freq[x]++;
+      }  
+      unordered_set<int>s;
+      for(auto x: freq){
+          s.insert(x.second);
+      }
+      return freq.size()==s.size();
+    }
+};
+ ```
+
+#### JAVA
+
+```JAVA
+class Solution {
+    public boolean uniqueOccurrences(int[] arr) {
+        Map<Integer, Integer> freq = new HashMap<>();
+        for (int x : arr) {
+            freq.put(x, freq.getOrDefault(x, 0) + 1);
+        }
+
+        Set<Integer> s = new HashSet<>();
+        for (int x : freq.values()) {
+            s.add(x);
+        }
+
+        return freq.size() == s.size();
+    }
+}
+```
+
+#### PYTHON
+
+```python
+class Solution:
+    def uniqueOccurrences(self, arr: List[int]) -> bool:
+        freq = {}
+        for x in arr:
+            freq[x] = freq.get(x, 0) + 1
+
+        return len(freq) == len(set(freq.values()))
+```
+
+
+
+### Complexity Analysis
+
+- Time Complexity: $O(n)$ 
+
+- Space Complexity: $O(n)$ 
+
+### References
+
+- **LeetCode Problem**: Unique Number of Occurrences