【leetcode】【单链表】【148】Sort List

#include<iostream>
using namespace std;

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

class Solution {
public:
	ListNode* merge(ListNode* l1, ListNode* l2){
		ListNode* temp = new ListNode(0);
		ListNode* cur = temp;
		while (l1&&l2){
			if (l1->val < l2->val){
				cur->next = l1;
				l1 = l1->next;
			}else{
				cur->next = l2;
				l2 = l2->next;
			}
			cur = cur->next;
		}
		if (l1)
			cur->next = l1;
		else
			cur->next = l2;
		cur = temp->next;
		temp->next = NULL;

		delete temp;
		return cur;
	}
	ListNode* mergeSort(ListNode* head){ //归并排序
		if (head == NULL || head->next == NULL)
			return head;
		ListNode* slow = head;
		ListNode* fast = head;
		ListNode* preSlow = NULL;
		while (fast&&fast->next){
			preSlow = slow;
			slow = slow->next;
			fast = fast->next->next;
		}
		preSlow->next = NULL;
		ListNode* lList = mergeSort(head);
		ListNode* rList = mergeSort(slow);
		return merge(lList, rList);
	}
	ListNode* sortList(ListNode* head) {
		if (head == NULL || head->next == NULL)
			return head;
		return mergeSort(head);
	}
	ListNode* createList(ListNode* head){
		int numOfNode;
		int value;
		cout << "please input number of listNode:";
		cin >> numOfNode;
		cin >> value;
		head = new ListNode(value);
		ListNode* cur = head;
		for (int i = 1; i < numOfNode; ++i){
			cin >> value;
			ListNode* temp = new ListNode(value);
			cur->next = temp;
			cur = temp;
		}
		return head;
	}
	void printNode(ListNode* head){
		ListNode* cur = head;
		while (cur){
			cout << cur->val << " ";
			cur = cur->next;
		}
		cout << endl;
	}
};

int main(){
	Solution solution;

	ListNode* head = NULL;
	head = solution.createList(head);
	solution.printNode(head);

	head = solution.sortList(head);
	solution.printNode(head);
	system("pause");
	return 0;
}