一道有意思的题目Intersection of Two Linked Lists（双指针）

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

这道题有两个链表，所以我们可以分别为两个链表设置指针，如果一个指针到头了就只想另外一条链表，最终两个指针肯定会指向同一个位置，那个位置就是两个链表相交的地方

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {        ListNode *a=headA,*b=headB;        while(a!=b)        {            a=a?a->next:headB;            b=b?b->next:headA;        }        return a;    }};