Add 380_Insert_Delete_GetRandom_O(1).java

Author: Sean Prashad

Design/380_Insert_Delete_GetRandom_O(1).java

@@ -0,0 +1,50 @@
+class RandomizedSet {
+ HashMap<Integer, Integer> hm;
+ ArrayList<Integer> keys;
+ Random generator;
+
+ /** Initialize your data structure here. */
+ public RandomizedSet() {
+ hm = new HashMap<Integer, Integer>();
+ keys = new ArrayList<Integer>();
+ generator = new Random();
+ }
+
+ /**
+ * Inserts a value to the set. Returns true if the set did not already contain
+ * the specified element.
+ */
+ public boolean insert(int val) {
+ boolean contains = hm.containsKey(val);
+
+ if (contains) {
+ return false;
+ }
+
+ keys.add(val);
+ hm.put(val, hm.getOrDefault(val, 0) + 1);
+ return true;
+ }
+
+ /**
+ * Removes a value from the set. Returns true if the set contained the specified
+ * element.
+ */
+ public boolean remove(int val) {
+ boolean contains = hm.containsKey(val);
+
+ if (!contains) {
+ return false;
+ }
+
+ keys.remove(new Integer(val));
+ hm.remove(val);
+ return true;
+ }
+
+ /** Get a random element from the set. */
+ public int getRandom() {
+ ;
+ return keys.get(generator.nextInt(hm.size()));
+ }
+}