이슈 #449에서 솔루션 추가

LeetCode/Insert_Delete_GetRandom_O1.cpp

@@ -0,0 +1,49 @@
+class RandomizedSet {
+public:
+    RandomizedSet() {}
+
+    bool insert(int val) {
+        if (valToIndex.find(val) != valToIndex.end()) {
+            return false;
+        }
+
+        values.push_back(val);
+        valToIndex[val] = values.size() - 1;
+
+        return true;
+    }
+
+    bool remove(int val) {
+        if (valToIndex.find(val) == valToIndex.end()) {
+            return false;
+        }
+
+        int lastElement = values.back();
+        int indexToRemove = valToIndex[val];
+
+        values[indexToRemove] = lastElement;
+        valToIndex[lastElement] = indexToRemove;
+
+        values.pop_back();
+        valToIndex.erase(val);
+
+        return true;
+    }
+
+    int getRandom() {
+        int randomindex = rand() % values.size();
+        return values[randomindex];
+    }
+
+private:
+    unordered_map<int, int> valToIndex;
+    vector<int> values;
+};
+
+/**
+ * Your RandomizedSet object will be instantiated and called as such:
+ * RandomizedSet* obj = new RandomizedSet();
+ * bool param_1 = obj->insert(val);
+ * bool param_2 = obj->remove(val);
+ * int param_3 = obj->getRandom();
+ */