Copy List with Random Pointer
A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.
Return a deep copy of the list.
Note:
You must return the copy of the given head as a reference to the cloned list.
思路一：哈希Map(Java)
class LinearSpaceApproach {
public RandomListNode copyRandomList(RandomListNode head) {
if (head == null) {
return null;
}
Map<RandomListNode, RandomListNode> cloneMap = new HashMap<RandomListNode, RandomListNode>();
RandomListNode curr = head;
while (curr != null) {
cloneMap.put(curr, new RandomListNode(curr.val));
curr = curr.next;
}
curr = head;
while (curr != null) {
cloneMap.get(curr).next = cloneMap.get(curr.next);
cloneMap.get(curr).random = cloneMap.get(curr.random);
curr = curr.next;
}
return cloneMap.get(head);
}
}
时间复杂度o(n),空间复杂度o(n)
思路二：Tricky one(C++)
class Solution {
public:
RandomListNode *copyRandomList(RandomListNode *head) {
if (head == NULL) return NULL;
for (RandomListNode* cur = head; cur != nullptr; ) {
RandomListNode* node = new RandomListNode(cur->val);
node->next = cur->next;
cur->next = node;
cur = node->next;
}
for (RandomListNode* cur = head; cur != nullptr; ) {
if (cur->random != NULL)
cur->next->random = cur->random->next;
else
cur->next->random = NULL;
cur = cur->next->next;
}
// 分拆两个单链表
RandomListNode dummy(-1);
for (RandomListNode* cur = head, *new_cur = &dummy;
cur != nullptr; ) {
new_cur->next = cur->next;
new_cur = new_cur->next;
cur->next = cur->next->next;
cur = cur->next;
}
return dummy.next;
}
};
时间复杂度o(n),空间复杂度o(1)