Create insert-delete-getrandom-o1.cpp

kamyu104 · web-flow · commit 5163e1503b75 · 2016-08-04T13:07:14.000+08:00
diff --git a/C++/insert-delete-getrandom-o1.cpp b/C++/insert-delete-getrandom-o1.cpp
@@ -0,0 +1,55 @@
+// Time:  O(1)
+// Space: O(n)
+
+class RandomizedSet {
+public:
+    /** Initialize your data structure here. */
+    RandomizedSet() {
+        
+    }
+    
+    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
+    bool insert(int val) {
+        if (used_.count(val)) {
+            return false;
+        }
+
+        set_.emplace_back(val);
+        used_[val] = set_.size() - 1;
+
+        return true;
+    }
+    
+    /** Removes a value from the set. Returns true if the set contained the specified element. */
+    bool remove(int val) {
+        if (!used_.count(val)) {
+            return false;
+        }
+
+        used_[set_.back()] = used_[val];
+        swap(set_[used_[val]], set_.back());
+
+        used_.erase(val);
+        set_.pop_back();
+
+        return true;
+    }
+    
+    /** Get a random element from the set. */
+    int getRandom() {
+        return set_[rand() % set_.size()];
+    }
+
+private:
+    vector<int> set_;
+    unordered_map<int, int> used_;
+};
+
+/**
+ * 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();
+ */
+ 
