leetcode707 设计链表-爱代码爱编程

前言

题目： 707. 设计链表
文档： 代码随想录——设计链表
编程语言： C++
解题状态： 代码功底不够，只能写个大概

思路

主要考察对链表结构的熟悉程度，对链表的增删改查，比较考验代码功底以及对链表的掌握。本题中的一些边界条件也要注意。

代码

class MyLinkedList {
public:
    struct ListNode {
        int val;
        ListNode* next;
        ListNode(int x) : val(x), next(nullptr) {}
    };

    MyLinkedList() {
        _dummyHead = new ListNode(0);
        _size = 0;
    }
    
    int get(int index) {
        if (index > (_size - 1) || index < 0) {
            return -1;
        }

        ListNode* cur = _dummyHead -> next;

        while (index--) {
            cur = cur -> next;
        }

        return cur -> val;
    }
    
    void addAtHead(int val) {
        ListNode* newNode = new ListNode(val);

        newNode -> next = _dummyHead -> next;
        _dummyHead -> next = newNode;

        _size++;
    }
    
    void addAtTail(int val) {
        ListNode* newNode = new ListNode(val);
        ListNode* cur = _dummyHead;

        while (cur -> next != nullptr) {
            cur = cur -> next;
        }
        cur -> next = newNode;

        _size++;
    }
    
    void addAtIndex(int index, int val) {
        if (index > _size) {
            return;
        }

        ListNode* newNode = new ListNode(val);
        ListNode* cur = _dummyHead;
        while (index--) {
            cur = cur -> next;
        }
        newNode -> next = cur -> next;
        cur -> next = newNode;

        _size++;
    }
    
    void deleteAtIndex(int index) {
        if (index >= _size || index < 0) {
            return;
        }

        ListNode* cur = _dummyHead;
        while (index--) {
            cur = cur -> next;
        }
        ListNode* tmp = cur -> next;
        cur -> next = cur -> next -> next;
        delete tmp;

        _size--;
    }

    void printLinkedList() {
        ListNode* cur = _dummyHead;
        while (cur -> next != nullptr) {
            cout << cur -> next -> val << " ";
            cur = cur -> next;
        }
        cout << endl;
    }

private:
    int _size;
    ListNode* _dummyHead;
};