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.
public class MyHashSet {
List<int>[] table;
const int size = 10000;
/** Initialize your data structure here. */
public MyHashSet() {
table = new List<int>[size];
}
public void Add(int key) {
if(Contains(key)){
return;
}
int hash = GetHash(key);
if(table[hash] == null){
table[hash]=new List<int>();
}
table[hash].Add(key);
}
public void Remove(int key) {
int hash = GetHash(key);
if(table[hash]==null){
return;
}
table[hash].Remove(key);
}
/** Returns true if this set contains the specified element */
public bool Contains(int key) {
int hash = GetHash(key);
if(table[hash]==null){
return false;
}
return table[hash].Contains(key);
}
private int GetHash(int key){
return (key * 7)%size;
}
}
/**
* Your MyHashSet object will be instantiated and called as such:
* MyHashSet obj = new MyHashSet();
* obj.Add(key);
* obj.Remove(key);
* bool param_3 = obj.Contains(key);
*/Time Complexity: O(1) Amortised time complexity
Space Complexity: O(n)
