Create Smallest Number in Infinite Set.java

Author: anthonyzhub

Smallest Number in Infinite Set.java

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+// https://leetcode.com/problems/smallest-number-in-infinite-set/
+
+class SmallestInfiniteSet {
+    
+    // Create a TreeSet and a variable to hold the smallest number
+    // NOTE: TreeSet is a self-balancing BST - similar to a Red-Black tree
+    TreeSet<Integer> set;
+    int smallestNum;
+
+    public SmallestInfiniteSet() {
+        
+        // Initialize class variables
+        set = new TreeSet<>();
+        smallestNum = 1;
+    }
+    
+    public int popSmallest() {
+        
+        // OBJECTIVE: Pop smallest element from set or return smallestNum
+        
+        // If tree isn't empty, pop head element
+        if (!set.isEmpty()) {
+            return set.pollFirst();
+        }
+        
+        // If tree is empty, return smallest number based on variable
+        smallestNum++;
+        return smallestNum - 1;
+    }
+    
+    public void addBack(int num) {
+        
+        // OBJECTIVE: Add num to tree if it doesn't exist
+        
+        // If num is less than smallestNum and doesn't exist in set, add it to set
+        if (num < smallestNum && !set.contains(num)) {
+            set.add(num);
+        }
+    }
+}
+
+/**
+ * Your SmallestInfiniteSet object will be instantiated and called as such:
+ * SmallestInfiniteSet obj = new SmallestInfiniteSet();
+ * int param_1 = obj.popSmallest();
+ * obj.addBack(num);
+ */