public void ListOf_2()
{
Node n2 = new Node() { Next = null, Val = 2 };
Node n1 = new Node() { Next = n2, Val = 1 };
PrintList(n1);
var node = ReverseRecursive(n1);
PrintList(node);
Assert.AreEqual(n2.Next.Val, n1.Val);
Assert.AreEqual(n1.Next, null);
}
void PrintList(Node node)
{
StringBuilder sb = new StringBuilder();
while (node != null)
{
sb.AppendFormat("{0}=>", node.Val);
node = node.Next;
}
sb.Append("null");
Console.WriteLine(sb.ToString());
Trace.WriteLine(sb.ToString());
}
public void ListOf5_Iterative()
{
Node n5 = new Node() { Next = null, Val = 5 };
Node n4 = new Node() { Next = n5, Val = 4 };
Node n3 = new Node() { Next = n4, Val = 3 };
Node n2 = new Node() { Next = n3, Val = 2 };
Node n1 = new Node() { Next = n2, Val = 1 };
PrintList(n1);
var node = ReverseIterative(n1);
PrintList(node);
Assert.AreEqual(n2.Next.Val, n1.Val);
Assert.AreEqual(n1.Next, null);
}
Node ReverseIterative(Node head)
{
Node prev, curr, next;
prev = null;
curr = head;
next = curr.Next;
while (curr != null && curr.Next != null)
{
curr.Next = prev;
prev = curr;
curr = next;
next = next.Next;
}
curr.Next = prev;
return curr;
}
public void Single()
{
Node n = new Node() { Next = null, Val = 1 };
ReverseRecursive(n);
}
Node ReverseRecursive(Node head)
{
if (head == null || head.Next == null)
{
return head;
}
Node headReveresed = ReverseRecursive(head.Next);
head.Next.Next = head;//we set the tail of the reversed to original head
head.Next = null; // original head is the tail of the revresed
return headReveresed;
}