36-两个链表的第一个公共节点

题目描述

输入两个链表，找出它们的第一个公共结点。（注意因为传入数据是链表，所以错误测试数据的提示是用其他方式显示的，保证传入数据是正确的）

代码：

/*
public class ListNode {
    int val;
    ListNode next = null;
    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
        public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
        int len1 = getListNodeLength(pHead1);
        int len2 = getListNodeLength(pHead2);
        int diff = Math.abs(len1 - len2);
        while (diff > 0) {
            if (len1 > len2) {
                pHead1 = pHead1.next;
            } else {
                pHead2 = pHead2.next;
            }
              diff--;
        }
        while (pHead1 != pHead2
                && pHead1 != null
                && pHead2 != null) {
            pHead1 = pHead1.next;
            pHead2 = pHead2.next;
        }
        return pHead1;
    }
    private int getListNodeLength(ListNode head) {
        int length = 0;
        while (head != null) {
            length += 1;
            head = head.next;
        }
        return length;
    }
}