LeetCode 705: Design HashSet Solution

Problem Explanation

Explanation:

To design a HashSet without using any built-in hash table libraries, we can implement a basic hash set using an array of booleans. We will use the key as the index in the array, and the value at that index will indicate whether the key exists in the set or not.

Algorithm:

Initialize an array of booleans of size 10^6 + 1 to represent the HashSet.
Implement the add(key) method by setting the value at index key to true.
Implement the contains(key) method by checking the value at index key and returning true if it is true, false otherwise.
Implement the remove(key) method by setting the value at index key to false.

Time Complexity:

The time complexity for all operations (add, remove, contains) is O(1) on average.

Space Complexity:

The space complexity is O(1) as we are using a fixed-size array.

Solution Code

class MyHashSet {
    boolean[] set;
    
    public MyHashSet() {
        set = new boolean[1000001];
    }
    
    public void add(int key) {
        set[key] = true;
    }
    
    public void remove(int key) {
        set[key] = false;
    }
    
    public boolean contains(int key) {
        return set[key];
    }
}

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705. Design HashSet