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  • leetCode(3):Intersection of Two Linked Lists 分类: leetCode 2015-06-16 14:41 124人阅读 评论(0) 收藏

    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.
    /**
     * 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) {
            if(headA==NULL || headB==NULL)
        		return NULL;
        	int a=0;
        	int b=0;
        	
        	ListNode* p=headA;
        	while(p)
        	{
        		a++;
        		p=p->next;
        	}
    		p=headB;
        	while(p)
        	{
        		b++;
        		p=p->next;
        	}
        	
        	int diff=a-b;
        	
        	ListNode* pA=headA;
        	ListNode* pB=headB;
        	
        	if(diff>=0)
        	{
        		int i=0;
        		while(i<diff)
        		{
        			pA=pA->next;
        			i++;
        		}
        	}
        	else
        	{
        		diff*=(-1);
        		int i=0;
        		while(i<diff)
        		{
        			pB=pB->next;
        			i++;
        		}
        	}	
        	while(pA!=pB && pA!=NULL)
        	{
        		pA=pA->next;
        		pB=pB->next;
        	}
        	if(pA==NULL)
        		return NULL;
        	else
        		return pA;	
                
            }
    };



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  • 原文地址:https://www.cnblogs.com/zclzqbx/p/4687114.html
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