Leetcode - Partition List

iteye_17352

于 2015-07-22 09:09:18 发布

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分类专栏： Two pointers 文章标签：数据结构与算法

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本文介绍了一种链表分隔算法，该算法将链表中小于给定值x的节点放置在大于等于x的节点之前，并保持各部分内部节点的原始顺序。通过创建两个辅助链表来实现这一目标，最后将这两个链表合并。

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Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

You should preserve the original relative order of the nodes in each of the two partitions.

For example,
Given 1->4->3->2->5->2 and x = 3,
return 1->2->2->4->3->5.

[分析] 想到创建两个辅助链表就好办了，small链表存储小于x的节点，large链表存储大于x的节点，最后merge两个链表。


public class Solution {
    public ListNode partition(ListNode head, int x) {
        ListNode small = new ListNode(-1);
        ListNode large = new ListNode(1);

        ListNode pSmall = small;
        ListNode pLarge = large;
        ListNode curr = head;
        while (curr != null) {
            if (curr.val < x) {
                pSmall.next = curr;
                pSmall = pSmall.next;
            } else {
                pLarge.next = curr;
                pLarge = pLarge.next;
            }
            curr = curr.next;
        }
        pLarge.next = null;
        pSmall.next = large.next;
        return small.next;
    }
}