Insert Delete GetRandom O(1)

Author: ishpreet-singh

Diff for: 12.cpp

@@ -0,0 +1,79 @@
+/*
+
+Insert Delete GetRandom O(1)
+----------------------------
+
+Design a data structure that supports all following operations in average O(1) time.
+
+insert(val): Inserts an item val to the set if not already present.
+remove(val): Removes an item val from the set if present.
+getRandom: Returns a random element from current set of elements. Each element must have the same probability of being returned.
+Example:
+
+// Init an empty set.
+RandomizedSet randomSet = new RandomizedSet();
+
+// Inserts 1 to the set. Returns true as 1 was inserted successfully.
+randomSet.insert(1);
+
+// Returns false as 2 does not exist in the set.
+randomSet.remove(2);
+
+// Inserts 2 to the set, returns true. Set now contains [1,2].
+randomSet.insert(2);
+
+// getRandom should return either 1 or 2 randomly.
+randomSet.getRandom();
+
+// Removes 1 from the set, returns true. Set now contains [2].
+randomSet.remove(1);
+
+// 2 was already in the set, so return false.
+randomSet.insert(2);
+
+// Since 2 is the only number in the set, getRandom always return 2.
+randomSet.getRandom();
+*/
+
+class RandomizedSet {
+public:
+    /** Initialize your data structure here. */
+    vector<int>arr;
+    map<int, int>mp;
+    RandomizedSet() {
+        
+    }
+    
+    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
+    bool insert(int val) {
+        if(mp.count(val))    return false;
+        mp[val] = arr.size();
+        arr.push_back(val);
+        return true;
+    }
+    
+    /** Removes a value from the set. Returns true if the set contained the specified element. */
+    bool remove(int val) {
+        if(!mp.count(val))    return false;
+        int index = mp.at(val);
+        mp[arr.back()] = index;
+        mp.erase(val);
+        swap(arr[index], arr.back());
+        arr.pop_back();
+        return true;
+    }
+    
+    /** Get a random element from the set. */
+    int getRandom() {
+        int index = rand() % arr.size();
+        return arr[index];
+    }
+};
+
+/**
+ * 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();
+ */

Diff for: README.md

@@ -12,4 +12,5 @@
 |   8  |          Power of Two          |  [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/8.cpp) |
 |   9  |         Is Subsequence         |  [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/9.cpp) |
 |  10  |     Search Insert Position     | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/10.cpp) |
-|  11  |           Sort Colors          | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/11.cpp) |
+|  11  |           Sort Colors          | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/11.cpp) |
+|  12  |  Insert Delete GetRandom O(1)  | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/12.cpp) |