705. Design HashSet

Problem

Tags: Array, Hash Table, Linked List, Design, Hash Function

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

Implement MyHashSet class:

• void add(key) Inserts the value key into the HashSet.
• bool contains(key) Returns whether the value key exists in the HashSet or not.
• void remove(key) Removes the value key in the HashSet. If key does not exist in the HashSet, do nothing.

Example 1:

Input
["MyHashSet", "add", "add", "contains", "contains", "add", "contains", "remove", "contains"]
[[], [1], [2], [1], [3], [2], [2], [2], [2]]
Output
[null, null, null, true, false, null, true, null, false]

Explanation
MyHashSet myHashSet = new MyHashSet();
myHashSet.add(1);      // set = [1]
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(1); // return True
myHashSet.contains(3); // return False, (not found)
myHashSet.add(2);      // set = [1, 2]
myHashSet.contains(2); // return True
myHashSet.remove(2);   // set = [1]
myHashSet.contains(2); // return False, (already removed)

Constraints:

• 0 <= key <= 10^6
• At most 10^4 calls will be made to add, remove, and contains.

Code

C

// 705. Design HashSet (1/9/54183)
// Runtime: 96 ms (85.58%) Memory: 25.04 MB (94.80%) 

// Macros and functions in sys/mman.h
extern void* mmap(void* addr, size_t len, int prot, int flags, int fd, off_t offset);
extern int munmap(void* addr, size_t len);

#define SIZE 1000001ULL

typedef struct {
    bool key[SIZE];
} MyHashSet;

MyHashSet* myHashSetCreate() {
    return mmap(NULL, sizeof(MyHashSet), 0b11, 0x22, -1, 0);
}

void myHashSetAdd(MyHashSet* this, int key) {
    this->key[key] = true;
}

void myHashSetRemove(MyHashSet* this, int key) {
    this->key[key] = false;
}

bool myHashSetContains(MyHashSet* this, int key) {
    return this->key[key];
}

void myHashSetFree(MyHashSet* this) {
    munmap(this, sizeof(MyHashSet));
}

/**
 * Your MyHashSet struct will be instantiated and called as such:
 * MyHashSet* obj = myHashSetCreate();
 * myHashSetAdd(obj, key);
 
 * myHashSetRemove(obj, key);
 
 * bool param_3 = myHashSetContains(obj, key);
 
 * myHashSetFree(obj);
*/