Middle of Linked List

Question:

Find the middle node of a linked list.

Example Given 1->2->3, return the node with value 2.

Given 1->2, return the node with value 1.

Code:

/**
 * Definition for ListNode
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param head: the head of linked list.
     * @return: a middle node of the linked list
     */
    public ListNode middleNode(ListNode head) { 
        // Write your code here
        // 好好审题
        // 想好初始化
        int length = 0;
        ListNode cur = head;
        while (cur != null) {
            length++;
            cur = cur.next;
        }
        int middle = (length + 1) / 2;
        cur = head;
        // return the pointing node,
        // middle = index + 1
        // so using (middle - 1 > 0)
        while (middle - 1 > 0) {
            cur = cur.next;
            // 必杀！while loop里面的循环条件变化
            middle--;
        }
        return cur;
    }
}