Java for 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.

解题思路：

先遍历两个list的长度，然后长的减去短的，之后同时遍历即可，JAVA实现如下：

    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA==null||headB==null)
        	return null;
        int lengthA=0,lengthB=0;
        ListNode tempA=headA,tempB=headB;
    	while(tempA!=null){
    		tempA=tempA.next;
    		lengthA++;
        }
    	while(tempB!=null){
    		tempB=tempB.next;
    		lengthB++;
        }
    	if(lengthB>lengthA){
    		tempA=headA;
    		headA=headB;
    		headB=tempA;
    		int temp=lengthA;
    		lengthA=lengthB;
    		lengthB=temp;
    	}
    	int length=lengthA-lengthB;
    	while(length-->0)
    		headA=headA.next;
    	while(headA!=null){
    		if(headA==headB)
    			return headA;
    		headA=headA.next;
    		headB=headB.next;
    	}
    	return headA; 
    }