剑指offer52：两个链表的第一个公共节点

1、题目

剑指offer52：两个链表的第一个公共节点

输入两个链表，找出它们的第一个公共节点。

2、代码

class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        ListNode A = headA;//指针A,先遍历A链表，再遍历B链表，直到走到第一个公共节点与B指针相遇，A指针步数为a+(b-c)
        ListNode B = headB;//指针B,先遍历B链表，再遍历A链表，直到走到第一个公共节点与A指针相遇，B指针步数为b+(a-c)

        //相遇原理：A指针和B指针按以上走到第一个公共节点时，均走a+b-c步。

        while (A != B){
            A = (A!=null) ? A.next : headB;
            B = (B!=null) ? B.next : headA;
        }

        return A;
    }
}

3、随笔

3.1、测试代码

public static void main(String[] args) {
        ListNode headA = new ListNode(4);
        ListNode firstNodeA = new ListNode(1);
        ListNode secondNodeA = new ListNode(8);
        ListNode thirdNodeA = new ListNode(4);
        ListNode fourthNodeA = new ListNode(5);

        headA.next = firstNodeA;
        firstNodeA.next = secondNodeA;
        secondNodeA.next = thirdNodeA;
        thirdNodeA.next = fourthNodeA;
        fourthNodeA.next = null;

    
        ListNode headB = new ListNode(5);
        ListNode firstNodeB = new ListNode(0);
        ListNode secondNodeB = new ListNode(1);

        headB.next = firstNodeB;
        firstNodeB.next = secondNodeB;
        secondNodeB.next = secondNodeA;
        
    
        ListNode result = getIntersectionNode(headA,headB);
        System.out.println("result.val = " + result.val);
    }