[刷题]Partition List

[LintCode]Partition List

/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */ 
public class Solution {
    /**
     * @param head: The first node of linked list.
     * @param x: an integer
     * @return: a ListNode 
     */
    public ListNode partition(ListNode head, int x) {
        // 2015-4-24
        if (head == null) {
            return head;
        }
        // 两个新的链表
        ListNode dummyA = new ListNode(0);
        ListNode nodeA = dummyA;
        ListNode dummyB = new ListNode(0);
        ListNode nodeB = dummyB;
        
        while (head != null) {
            if (head.val < x) {
                nodeA.next = head;
                nodeA = nodeA.next;
            } else {
                nodeB.next = head;
                nodeB = nodeB.next;
            }
            head = head.next;
        }
        nodeA.next = dummyB.next;
        nodeB.next = null;
        return dummyA.next;
    }
}