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  • Leetcode45: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.
    /**
     * 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) {
          <span style="white-space:pre">	</span>int lenA = 0;
    	int lenB = 0;
    	ListNode *head1 = headA;
    <span style="white-space:pre">	</span>ListNode *head2 = headB;
    	while (head1!=NULL)
    	{
    		head1 = head1->next;
    		lenA++;
    	}
    	while (head2!=NULL)
    	{
    		head2 = head2->next;
    		lenB++;
    	}
    	int n;
    	if (lenA < lenB)
    	{
    		n = lenB - lenA;
    		head1 = headA;
    		head2 = headB;
    		for (int i = 0; i < n; i++)
    		{
    			head2 = head2->next;
    		}
    	}
    	else
    	{
    		n = lenA - lenB;
    		head1 = headA;
    		head2 = headB;
    		for (int i = 0; i < n; i++)
    		{
    			head1 = head1->next;
    		}
    	}
    
    	while (head1 != head2)
    	{
    		head1 = head1->next;
    		head2 = head2->next;
    	}
    
    	return head1;
        }
    };


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  • 原文地址:https://www.cnblogs.com/yutingliuyl/p/6886178.html
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