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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.

 

求两个链表的交集。这里应该注意,如果在一个节点两个链表相交了,那么之后的节点也是相交的,所以我们可以这么做:

扫描到链表A或者链表B的末尾时,将A的尾部指针指向B的头,将B的尾部指针指向A的头,知道找到相同的节点

/** * 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 *p1 = headA;        ListNode *p2 = headB;        bool mark1 = false;        bool mark2 = false;        while(p1 != nullptr && p2 != nullptr) {            if (p1 == p2) return p1;            p1 = p1->next;            p2 = p2->next;            if (p1 == nullptr && !mark1) p1 = headB,mark1 = true;            if (p2 == nullptr && !mark2) p2 = headA,mark2 = true;        }        return nullptr;    }};

 

160. Intersection of Two Linked Lists