单链表排序

快排：

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param head ListNode类 the head node
     * @return ListNode类
     */
    ListNode* solve(ListNode* head, ListNode* pend){
        if(head==NULL||head->next==pend) return head;
        int val = head->val;
        ListNode* p = head;
        ListNode* q = p->next;
        while(q!=pend){
            if(q->val < val){
                p = p->next;
                swap(p->val, q->val);
            }
            q = q->next;
        }
        swap(head->val, p->val);
        return p;
    }
 
    void quick_sort(ListNode* head, ListNode* pend){
        if(head==pend) return;
        ListNode* p = solve(head, pend);//找出枢轴
        quick_sort(head, p);
        quick_sort(p->next, pend);
    }
 
    ListNode* sortInList(ListNode* head) {
        // write code here
        quick_sort(head, NULL);
        return head;
    }
};

利用vector和sort进行排序

class Solution {
public:
    /**
     *
     * @param head ListNode类 the head node
     * @return ListNode类
     */
    ListNode* sortInList(ListNode* head) {
        vector<int> vec;
        ListNode* cur = head;
        // 1.构建vector
        while(cur) {
            vec.push_back(cur->val);
            cur = cur->next;
        }
        // 2.vector排序
        sort(vec.begin(), vec.end());
        // 3.构建链表
        ListNode* dummy = new ListNode(0);
        ListNode* res = new ListNode(0);
        dummy->next = res;
        for(int i : vec) {
            res->next = new ListNode(i);
            res = res->next;
        }
        res->next = nullptr;
        return dummy->next->next;
    }
};