public RandomListNode CopyRandomList2(RandomListNode head)
{
if (head == null)// my bug
{
return(head);
}
var map = new Dictionary <RandomListNode, RandomListNode>();
// loop 1. copy all the nodes
RandomListNode node = head;
while (node != null)
{
map[node] = new RandomListNode(node.label);
node = node.next;
}
// loop 2. assign next and random pointers
node = head;
while (node != null)
{
if (node.next != null)
{
map[node].next = map[node.next];
}
if (node.random != null)
{
map[node].random = map[node.random];
}
node = node.next;
}
return(map[head]);
}
public RandomListNode CopyRandomList(RandomListNode head)
{
if (head == null)// my bug
{
return(head);
}
var iter = head;
// First round: make copy of each node,
// and link them together side-by-side in a single list.
while (iter != null)
{
var 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 copy2, copyIter = pseudoHead;
while (iter != null)
{
var next = iter.next.next;
// extract the copy
copy2 = iter.next;
copyIter.next = copy2;
copyIter = copy2;
// restore the original list
iter.next = next;
iter = next;
}
return(pseudoHead.next);
}