day-124.cpp

/*
  Design HashSet

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.
*/

// Easy solution using vector with 1e6 items in it
class MyHashSet {
   public:
    vector<int> hashSet;
    MyHashSet() { hashSet = vector<int>(int(1e6), 0); }

    void add(int key) {
        if (hashSet[key]) return;
        hashSet[key] = 1;
    }

    void remove(int key) {
        if (hashSet[key] == 0) return;
        hashSet[key] = 0;
    }

    /** Returns true if this set contains the specified element */
    bool contains(int key) {
        if (hashSet[key]) return true;
        return false;
    }
};