leetcode-707链表的设计

链表的设计

这里链表的设计真是坎坷，虽然是基本操作，但真是花了不好时间，翻看了很多别的写的链表设计，借用了一些思路，终于提交通过了，不容易。上代码吧。

class MyLinkedList {
public:
    /** Initialize your data structure here. */
    MyLinkedList() {
       LinkedList = 0;
    } 
    ListNode *LinkedList;
    /** Get the value of the index-th node in the linked list. If the index is invalid, return -1. */
    int get(int index) {
        int i = 0;
		ListNode *head = LinkedList;
		while (head&&i<index) {
			head = head->next;
			i++;
		}
		if (head&&i == index) 
            return head->val;
		else return -1;
    }
    /** Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list. */
    void addAtHead(int val) {
        ListNode *newnode =new ListNode(val);
        newnode->next=LinkedList;
        LinkedList=newnode;
    }
    
    /** Append a node of value val to the last element of the linked list. */
    void addAtTail(int val) {
        ListNode *newnode=new ListNode(val);
        newnode->next=NULL;
        ListNode *head = LinkedList;
        if (!head) {
			LinkedList = newnode;
			return;
		}
		while (head&&head->next) {
			head = head->next;
		}
		head->next =  newnode;
    }
    /** Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted. */
    void addAtIndex(int index, int val) {
        int i = 0;
		ListNode *head = LinkedList;
		if (!head&&index==0) {
			ListNode *newnode =new ListNode(val);
			newnode->next = 0;
			LinkedList =newnode;
			return;
		}
		while (head&&i<index - 1) {
			head = head->next;
			i++;
		}
		if (head&&head->next == 0) {
			ListNode *newnode =new ListNode(val);
			newnode->next = 0;
			head->next = newnode;
		}
		else if (i == index - 1 && head&&head->next) {
			ListNode *newnode =new ListNode(val);
			newnode->next = head->next;
			head->next = newnode;
		}
    }
    /** Delete the index-th node in the linked list, if the index is valid. */
    void deleteAtIndex(int index) {
     ListNode *head = LinkedList;
		int i = 0;
		while (head&&i<index-1) {
			head = head->next;
			i++;
		}
		if (head == 0) return;
		if (head->next == 0 && index == 0) {//只有一个节点的情况
			LinkedList = 0;
			return;
		}
		if (head->next) {
			ListNode *tmp = head->next;
			head->next = tmp->next;
			free(tmp);
		}
	}
};