Question
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.
Solution using Hash Map
TODO
Code
public class Solution {
public RandomListNode copyRandomList(RandomListNode head) {
if (head == null) {
return null;
}
final Map<RandomListNode, RandomListNode> map = new HashMap<RandomListNode, RandomListNode>();
RandomListNode cur = head;
while(cur != null) {
map.put(cur, new RandomListNode(cur.label));
cur = cur.next;
}
for (Map.Entry<RandomListNode, RandomListNode> entry : map.entrySet()) {
final RandomListNode newNode = entry.getValue();
newNode.next = map.get(entry.getKey().next);
newNode.random = map.get(entry.getKey().random);
}
return map.get(head);
}
}
Performance
TODO
O(1) Space Solution
TODO
Code
public RandomListNode copyRandomList(RandomListNode head) {
RandomListNode iter = head, next;
// First round: make copy of each node,
// and link them together side-by-side in a single list.
while (iter != null) {
next = iter.next;
RandomListNode copy = new RandomListNode(iter.label);
iter.next = copy;
copy.next = next;
iter = next;
}
// Second round: assign random pointers for the copy nodes.
iter = head;
while (iter != null) {
if (iter.random != null) {
iter.next.random = iter.random.next;
}
iter = iter.next.next;
}
// Third round: restore the original list, and extract the copy list.
iter = head;
RandomListNode pseudoHead = new RandomListNode(0);
RandomListNode copy, copyIter = pseudoHead;
while (iter != null) {
next = iter.next.next;
// extract the copy
copy = iter.next;
copyIter.next = copy;
copyIter = copy;
// restore the original list
iter.next = next;
iter = next;
}
return pseudoHead.next;
}
Performance
TODO