QUESTION:

Design a HashSet without using any built-in hash table libraries.

To be specific, your design should include these functions:

add(value): Insert a value into the HashSet. contains(value) : Return whether the value exists in the HashSet or not. remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.

Example:

MyHashSet hashSet = new MyHashSet(); hashSet.add(1);
hashSet.add(2);
hashSet.contains(1); // returns true hashSet.contains(3); // returns false (not found) hashSet.add(2);
hashSet.contains(2); // returns true hashSet.remove(2);
hashSet.contains(2); // returns false (already removed)

Note:

All values will be in the range of [0, 1000000]. The number of operations will be in the range of [1, 10000]. Please do not use the built-in HashSet library.

EXPLANATION:

这个不想多说，采用了一个讨巧的方式。

SOLUTION:

class MyHashSet {
        boolean[] values = new boolean[1000001];

        /** Initialize your data structure here. */
        public MyHashSet() {
            Arrays.fill(values,false);
        }

        public void add(int key) {
            values[key] = true;
        }

        public void remove(int key) {
            values[key] = false;
        }

        /** Returns true if this set contains the specified element */
        public boolean contains(int key) {
            return values[key];
        }
}