题解 | #两个链表的第一个公共结点#

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    // 由于公共部分在链表后面，所以先统计长度， 然后移动长的节点，保证2个节点长度相同，在同时比较。
    public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
         int h1 = 0;
        int h2 = 0;
        for (ListNode node = pHead1; node != null; node = node.next) {
            h1++;
        }
        for (ListNode node = pHead2; node != null; node = node.next) {
            h2++;
        }
        ListNode cu2 = pHead2;
        ListNode cu1 = pHead1;
        int i = 0;
        if (h1 < h2) {
            while (i < h2 - h1) {
                cu2 = cu2.next;
                i++;
            }
        }
        int j = 0;
        if (h1 > h2) {
            while (j < h1 - h2) {
                cu1 = cu1.next;
                j++;
            }
        }
        while (cu1 != null && cu2 != null) {
            if (cu1.val == cu2.val) {
                return cu1;
            }
            cu1 = cu1.next;
            cu2 = cu2.next;
        }
        return null;
    }
}