Series articles

【 Brother hero training in July 】 The first 01 God : Array

【 Brother hero training in July 】 The first 02 God : character string

【 Brother hero training in July 】 The first 03 God : Sort

【 Brother hero training in July 】 The first 04 God : greedy

【 Brother hero training in July 】 The first 05 God : Double pointer

【 Brother hero training in July 】 The first 06 God : The sliding window

【 Brother hero training in July 】 The first 07 God : Hashtable

【 Brother hero training in July 】 The first 08 God : The prefix and

【 Brother hero training in July 】 The first 09 God : Two points search

【 Brother hero training in July 】 The first 10 God : An operation

【 Brother hero training in July 】 The first 11 God ： matrix

【 Brother hero training in July 】 The first 12 God ： Linked list

【 Brother hero training in July 】 The first 13 God ： Double linked list

【 Brother hero training in July 】 The first 14 God ： Stack

【 Brother hero training in July 】 The first 15 God ： Depth-first search

【 Brother hero training in July 】 The first 16 God ： queue

【 Brother hero training in July 】 The first 17 God ： Breadth first search

【 Brother hero training in July 】 The first 18 God ： Trees

【 Brother hero training in July 】 The first 19 God ： Binary tree

【 Brother hero training in July 】 The first 20 God ： Search binary trees

【 Brother hero training in July 】 The first 21 God ： Pile up

One 、2336. The smallest number in an infinite set

2336. The smallest number in an infinite set

There is a set containing all positive integers [1, 2, 3, 4, 5, …] .
Realization SmallestInfiniteSet class ：
SmallestInfiniteSet() initialization SmallestInfiniteSet Object to contain all Positive integer .
int popSmallest() remove And return the smallest integer in the infinite set .
void addBack(int num) If it's a positive integer num No Exist in infinite set , Then a num add to To the infinite set .

leetcode2236 java

Ideas

1. The title is infinite set , Then we construct finite sets complementary to infinite sets

2. Infinite sets add Elements , Then finite set remove Elements

3. Infinite sets remove Elements , Then finite set add Elements

4. Infinite set removes and returns the smallest integer in the infinite set , For a finite set, it is add Elements , And return the smallest element that is not in the finite set

class SmallestInfiniteSet {
    
    HashSet<Integer> res;

    public SmallestInfiniteSet() {
    
        res = new HashSet<>();
    }
    
    public int popSmallest() {
    
        int count = 1;
        while(res.contains(count)){
    
            count++;
        }
        res.add(count);
        return count;


    }
    
    public void addBack(int num) {
    
        if(res.contains(num)) res.remove(num);
    }
}

summary