LeetCode Partition List

最新推荐文章于 2019-07-16 09:33:43 发布

原创最新推荐文章于 2019-07-16 09:33:43 发布 · 273 阅读

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本文介绍了一种链表分区算法，该算法将链表中小于给定值x的所有节点置于大于等于x的节点之前，同时保持各分区内的相对顺序不变。以输入1->4->3->2->5->2及x=3为例，返回结果为1->2->2->4->3->5。

题目：

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.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *partition(ListNode *head, int x) {
        ListNode *dummy1 = new ListNode(-1);
        ListNode *dummy2 = new ListNode(-1);
        ListNode *cur1 = dummy1, *cur2 = dummy2;
        while(head != NULL) {
            if(head->val < x) {
                cur1->next = head;
                cur1 = head;
            }
            else {
                cur2->next = head;
                cur2 = head;
            }
            head = head->next;
        }
        cur1->next = dummy2->next;
        cur2->next = NULL;
        head = dummy1->next;
        delete dummy1;
        delete dummy2;
        return head;
    }
};