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| class FirstUnique {
static class Node {
int val;
Node prev;
Node next;
Node(int _val) {
this.val = _val;
prev = null;
next = null;
}
}
private void removeNode(Node node) {
Node prevNode = node.prev;
Node nextNode = node.next;
if (prevNode == null && nextNode == null) {
head = null;
tail = null;
} else if (prevNode == null) {
head = nextNode;
head.prev = null;
} else if (nextNode == null) {
tail = prevNode;
tail.next = null;
} else {
prevNode.next = nextNode;
nextNode.prev = prevNode;
}
node.prev = null;
node.next = null;
}
private void insertNode(Node node) {
if (head == null) {
head = node;
tail = node;
} else {
tail.next = node;
node.prev = tail;
tail = node;
}
}
private Node head;
private Node tail;
private Map<Integer, Node> nodeMap;
private Set<Integer> duplicates;
public FirstUnique(int[] nums) {
nodeMap = new HashMap<>();
duplicates = new HashSet<>();
for (int num : nums) {
add(num);
}
}
public int showFirstUnique() {
if (nodeMap.isEmpty()) {
return -1;
}
return head.val;
}
public void add(int value) {
Node head = this.head;
Node tail = this.tail;
Map<Integer, Node> nodeMap = this.nodeMap;
if (nodeMap.containsKey(value)) {
removeNode(nodeMap.get(value));
nodeMap.remove(value);
duplicates.add(value);
} else if (!duplicates.contains(value)) {
Node newNode = new Node(value);
nodeMap.put(value, newNode);
insertNode(newNode);
}
head = this.head;
tail = this.tail;
}
}
|
bug找了好久.25行, tail转移的时候要把新的tail的next声明为null才行. 22行新head要把自己的prev设置为null. 否则就会出错. 比如移除最后一个node时, 新tail还指向旧的node, 这会让remove的逻辑出错, 误以为我们此时的tail不是tail, head的prev如果不指向null也会有一样的问题.
时间复杂度: O(1)
空间复杂度: O(n) 需要存nodes, map以及set.
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| class FirstUnique {
Set<Integer> unique;
Set<Integer> multiple;
public FirstUnique(int[] nums) {
unique = new LinkedHashSet<>();
multiple = new HashSet<>();
for (int num : nums) {
add(num);
}
}
public int showFirstUnique() {
return unique.isEmpty() ? -1 : unique.iterator().next();
}
public void add(int value) {
if (unique.contains(value)) {
unique.remove(value);
multiple.add(value);
} else if (!multiple.contains(value)) {
unique.add(value);
}
}
}
|
LinkedHashSet的写法.
时间复杂度和空间复杂度不变.
