Merge pull request #163 from FazeelUsmani/insert-delete-getRandom-in-O(1)-time-1

Create 21_insertDelRandom.cpp

Author: abdulbasith007

10 October LeetCode Challenge 2021/21_insertDelRandom.cpp

@@ -0,0 +1,52 @@
+class RandomizedSet {
+public:
+    void swap(int &a, int &b){
+        int temp = b;
+        b = a;
+        a = temp;
+    }
+    vector<int> A;
+    unordered_map<int, int> umap;    
+    /** Initialize your data structure here. */
+    RandomizedSet() {
+        A.clear();
+        umap.clear();
+    }
+    
+    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
+    bool insert(int val) {
+        if (umap.find(val) != umap.end())
+            return false;
+        A.push_back(val);
+        umap.insert(pair<int, int>(val, A.size() - 1));        
+        
+        return true;        
+    }
+    
+    /** Removes a value from the set. Returns true if the set contained the specified element. */
+    bool remove(int val) {        
+        if (umap.find(val) == umap.end())
+            return false;
+        
+        int index = umap[val];
+        A[index] = A[A.size()-1];
+        umap[A[index]] = index;        
+        A.pop_back();        
+        umap.erase(val);
+    
+        return true;
+    }
+    
+    /** Get a random element from the set. */
+    int getRandom() {
+        return A[rand() % A.size()];
+    }
+};
+
+/**
+ * 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();
+ */