Package g2301_2400.s2336_smallest_number_in_infinite_set

Class SmallestInfiniteSet

  • public class SmallestInfiniteSet
extends Object
    2336 - Smallest Number in Infinite Set.

    Medium

    You have a set which contains all positive integers [1, 2, 3, 4, 5, ...].

    Implement the SmallestInfiniteSet class:

    • SmallestInfiniteSet() Initializes the SmallestInfiniteSet object to contain all positive integers.
    • int popSmallest() Removes and returns the smallest integer contained in the infinite set.
    • void addBack(int num) Adds a positive integer num back into the infinite set, if it is not already in the infinite set.

    Example 1:

    Input

    [“SmallestInfiniteSet”, “addBack”, “popSmallest”, “popSmallest”, “popSmallest”, “addBack”, “popSmallest”, “popSmallest”, “popSmallest”]

    [ [], [2], [], [], [], [1], [], [], []]

    Output:

    [null, null, 1, 2, 3, null, 1, 4, 5]

    Explanation:

     SmallestInfiniteSet smallestInfiniteSet = new SmallestInfiniteSet();
 smallestInfiniteSet.addBack(2); // 2 is already in the set, so no change is made.
 smallestInfiniteSet.popSmallest(); // return 1, since 1 is the smallest number, and remove it from the set.
 smallestInfiniteSet.popSmallest(); // return 2, and remove it from the set.
 smallestInfiniteSet.popSmallest(); // return 3, and remove it from the set.
 smallestInfiniteSet.addBack(1); // 1 is added back to the set.
 smallestInfiniteSet.popSmallest(); // return 1, since 1 was added back to the set and
                                    // is the smallest number, and remove it from the set.
 smallestInfiniteSet.popSmallest(); // return 4, and remove it from the set.
 smallestInfiniteSet.popSmallest(); // return 5, and remove it from the set.

    Constraints:

    • 1 <= num <= 1000
    • At most 1000 calls will be made in total to popSmallest and addBack.

    • Constructor Detail

      • SmallestInfiniteSet

        public SmallestInfiniteSet()

    • Method Detail

      • popSmallest

        public int popSmallest()

      • addBack

        public void addBack​(int num)