leetcode 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.

 

也挺简单的，不过我比较粗心，还是很多小细节没有注意。每次变量一多，我就快烦死了== 

刚开始取得两个列表的长度，要对其才可以判断。其他的没有什么注意的点了。

/**
 * 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) {
        int lengthA=0,lengthB=0,d=0;
        ListNode* tempA=headA,*tempB=headB;
        while(tempA!=NULL){lengthA++;tempA=tempA->next;}
        while(tempB!=NULL){lengthB++;tempB=tempB->next;}
        tempA=headA;tempB=headB;
        if(lengthA>lengthB){
            d=lengthA-lengthB;
            while(d--) tempA=tempA->next;
        }
        else{
            d=lengthB-lengthA;
            while(d--) tempB=tempB->next;
        }
        d=min(lengthA,lengthB);
        while(d--){
            if(tempA==tempB) return tempA;
            else{ tempA=tempA->next;
                  tempB=tempB->next;}
        }
        return NULL;
        
        
    }
};