Leetcode 86. Partition List (链表好题)

  1. Partition List
    Medium

Given the head of 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.

Example 1:

Input: head = [1,4,3,2,5,2], x = 3

Output: [1,2,2,4,3,5]

Example 2:

Input: head = [2,1], x = 2

Output: [1,2]

Constraints:

The number of nodes in the list is in the range [0, 200].

-100 <= Node.val <= 100

-200 <= x <= 200

解法1:

注意不能直接用node=node->next。

复制代码
        ListNode *tmp = node->next;
        //node = node->next;
        node->next = NULL;
        node = tmp;

以 [1,4,3,2,5,2] 为例,5后面是2,如果不断开,就会形成环。

cpp 复制代码
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* partition(ListNode* head, int x) {
        ListNode *dummy1 = new ListNode(0), *dummy2 = new ListNode(0);
        ListNode *node1 = dummy1, *node2 = dummy2, *node = head;
        while (node) {
            if (node->val < x) {
                node1->next = node;
                node1 = node1->next;
            } else {
                node2->next = node;
                node2 = node2->next;
            }
            ListNode *tmp = node->next;
            //node = node->next;
            node->next = NULL;
            node = tmp;
        }
        node1->next = dummy2->next;
        ListNode *res = dummy1->next;
        delete(dummy1); delete(dummy2);
        return res;
    }
};
相关推荐
dragoooon341 小时前
[数据结构——lesson5.1链表的应用]
数据结构·链表
1白天的黑夜13 小时前
哈希表-49.字母异位词分组-力扣(LeetCode)
c++·leetcode·哈希表
愚润求学4 小时前
【贪心算法】day7
c++·算法·leetcode·贪心算法
逍遥德5 小时前
Java8 Comparator接口 和 List Steam 排序使用案例
java·spring boot·list·排序算法
言之。5 小时前
Django高效查询:values_list实战详解
django·sqlite·list
tju新生代魔迷18 小时前
数据结构:双向链表
数据结构·链表
学c语言的枫子20 小时前
数据结构——双向链表
c语言·数据结构·链表
共享家95271 天前
优先搜索(DFS)实战
算法·leetcode·深度优先
flashlight_hi1 天前
LeetCode 分类刷题:2563. 统计公平数对的数目
python·算法·leetcode
楼田莉子1 天前
C++算法专题学习:栈相关的算法
开发语言·c++·算法·leetcode