Design HashSet
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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)
1 class MyHashSet 2 final ListNode[] nodes = new ListNode[10000]; 3 /** Initialize your data structure here. */ 4 public MyHashSet() 5 6 7 8 public void add(int key) 9 int i = idx(key); 10 ListNode first = nodes[i]; 11 if (first == null) 12 nodes[i] = new ListNode(key); 13 else if (!exists(first, key)) 14 ListNode newNode = new ListNode(key); 15 newNode.next = nodes[i]; 16 nodes[i] = newNode; 17 18 19 20 public void remove(int key) 21 int i = idx(key); 22 if (nodes[i] == null) 23 return; 24 25 ListNode current = nodes[i]; 26 ListNode previous = null; 27 while (current != null) 28 if (current.key == key) 29 if (previous != null) 30 previous.next = current.next; 31 else 32 nodes[i] = current.next; 33 34 break; 35 else 36 previous = current; 37 current = current.next; 38 39 40 41 42 /** Returns true if this set contains the specified element */ 43 public boolean contains(int key) 44 int i = idx(key); 45 ListNode first = nodes[i]; 46 if (first == null) 47 return false; 48 49 return exists(first, key); 50 51 52 int idx(int key) 53 return key % nodes.length; 54 55 56 private boolean exists(ListNode node, int key) 57 ListNode current = node; 58 while (current != null) 59 if (current.key == key) 60 return true; 61 62 current = current.next; 63 64 return false; 65 66 67 68 69 class ListNode 70 int key; 71 ListNode next; 72 73 ListNode(int key) 74 this.key = key; 75 76
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