技術標籤：LeetCodejavaleetcode連結串列

https://leetcode-cn.com/problems/intersection-of-two-linked-lists/

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class
 
 Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA==null||headB==null)
            return null;
        ListNode a=headA,b=headB;

        while(a!=null&&b!=null){
            a=a.next;
            b=b.next;
        }
        int count1=0;
        int
 
 count2=0;
        while(a!=null){
            count1++;
            a=a.next;
        }
        while(b!=null){
            count2++;
            b=b.next;
        }
        a=headA;
        b=headB;
        while(count1>0){
            a=a.next;
		    count1--;
        }
        while(count2>0)
 
{
            b=b.next;
		    count2--;
        }
        while(a!=null&&a!=b){
            a=a.next;
            b=b.next;
        }
        return a;
    }
}

O(n) 時間複雜度，且僅用 O(1) 記憶體。