leetcode_160_Intersection of Two Linked Lists

Write a program to find the node at which the intersection of two singly linked lists begins.

For example, the following two linked lists:

A:          a1 → a2
                   ↘
                     c1 → c2 → c3
                   ↗            
B:     b1 → b2 → b3

begin to intersect at node c1.

Notes:

• If the two linked lists have no intersection at all, return null.
• The linked lists must retain their original structure after the function returns.
• You may assume there are no cycles anywhere in the entire linked structure.
• Your code should preferably run in O(n) time and use only O(1) memory.

Credits:
Special thanks to @stellari for adding this problem and creating all test cases.

public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
		if(headA==null||headB==null)
			return null;
        ListNode tempListNode=null;
        HashSet<ListNode>set=new HashSet<ListNode>();
        ListNode pListNode=headA;
        while(pListNode!=null)
        {
        	set.add(pListNode);
        	pListNode=pListNode.next;
        }
        pListNode=headB;
        while(pListNode!=null)
        {
        	if(set.contains(pListNode))
        	{
        		tempListNode=pListNode;
        		break;
        	}else
        	{
        		pListNode=pListNode.next;
        	}
        }
        return tempListNode;
    }