adding set leetcode problem

leetcode/p1207_unique_number_occurrence.cpp

@@ -0,0 +1,26 @@
+class Solution {
+public:
+    bool uniqueOccurrences(vector<int>& arr) {
+        int size = arr.size();
+        // key: number, value: occurrence
+        std::map<int, int> map1;
+        std::set<int> set1;
+        // create the map
+        for(int i=0; i<size; i++){
+            map1[arr[i]]++;
+        }
+        // use the map
+        std::map<int, int>::iterator itr;
+        itr = map1.begin();
+        while(itr != map1.end()){
+            // if this number of occurrence already exists
+            if(set1.find(itr->second) != set1.end()){
+                return false;
+            }
+            // otherwise, store it.
+            set1.insert(itr->second);
+            itr++;
+        }
+        return true;
+    }
+};