链表排序

https://leetcode.com/problems/insertion-sort-list/description/

1、归并排序：

#include <bits/stdc++.h>
#include "table.h"
using namespace std;
typedef long long int LL;

struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};


class Solution {
public:
    ListNode* findMid(ListNode *head) {
        if (head == NULL || head->next == NULL) return head;

        ListNode *slow = head, *fast = head->next;
        while (fast && fast->next) {
            slow = slow->next;
            fast = fast->next->next;
        }
        ListNode *tmp = slow->next;
        slow->next = NULL;
        return tmp;
    }

    ListNode* merge(ListNode* one, ListNode* two) {
        ListNode *first = NULL;
        if (one->val < two->val) {
            first = one;
            one = one->next;
        } else {
            first = two;
            two = two->next;
        }

        ListNode *ans = first;
        while (one && two) {
            if (one->val < two->val) {
                first->next = one;
                one = one->next;
            } else {
                first->next = two;
                two = two->next;
            }
            first = first->next;
        }
        while (one) {
            first->next = one;
            one = one->next;
            first = first->next;
        }
        while (two) {
            first->next = two;
            two = two->next;
            first = first->next;
        }
        return ans;
    }

    ListNode* guibin(ListNode* head) {
        if (head == NULL || head->next == NULL) return head;
        if (head->next->next == NULL) {
            if (head->val > head->next->val) {
                swap(head->val, head->next->val);
            }
            return head;
        }
        ListNode* mid = findMid(head);
        ListNode* one = guibin(head);
        ListNode* two = guibin(mid);
        return merge(one, two);
    }

    ListNode* insertionSortList(ListNode* head) {
        return guibin(head);
    }
};

void work() {
    int a[] = {4, 1, 2, 3, 5, 8};
    int len = sizeof(a) / sizeof(a[0]);
    ListNode* first = new ListNode(a[0]);
    ListNode* tmp = first;
    for (int i = 1; i < len; ++i) {
        first->next = new ListNode(a[i]);
        first = first->next;
    }
    tmp = t.insertionSortList(tmp);
    while (tmp) {
        printf("%d
", tmp->val);
        tmp = tmp->next;
    }
}

int main() {
    work();
    return 0;
}