leetcode707设计链表

悠悠 2022-10-06 09:56 101阅读 0赞

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTY3MjQwNA_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTY3MjQwNA_size_16_color_FFFFFF_t_70 1]  
思路：

1.  Node，注意Node的默认初始化
2.  MyLinkedList，我比较喜欢设计一个头节点（可以使(编号–)刚好在该节点的前一个位置），然后是list节点数量
3.  其他的操作没啥差别

代码

class Node{ 
    public:
        int val;
        Node *next;
        Node(){ }
        Node(int x):val(x),next(nullptr){ }
        Node(int x,Node* n):val(x),next(n){ }
    };
    
    class MyLinkedList { 
    private:
        int num ;
        Node *head;
    
    public:
        /** Initialize your data structure here. */
        MyLinkedList() { 
            num = 0;
            head = new Node(-1);
        }
        
        /** Get the value of the index-th node in the linked list. If the index is invalid, return -1. */
        int get(int index) { 
            if(index>(num-1)||num==0)
                return -1;
            Node *p=head->next;
            while (index--)
                p=p->next;
            return p->val;
        }
        
        /** 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) { 
            Node *NewNode = new Node(val,head->next);
            head->next = NewNode;
            num++;
        }
        
        /** Append a node of value val to the last element of the linked list. */
        void addAtTail(int val) { 
            Node *p=head;
            while(p->next){ 
                p=p->next;
            }
            Node *NewNode = new Node(val);
            p->next = NewNode;
            num++;
        }
        
        /** 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) { 
            Node *p = head;
            if(index>num)
                return;
            if(index<0){ 
                addAtHead(val);
                return;
            }
            if(index==num){ 
                addAtTail(val);
                return;
            }
            while(index--){ 
                p = p->next;
            }
            Node *NewNode = new Node(val);
            NewNode->next = p->next;
            p->next = NewNode;
            num++;
    
    
        }
        
        /** Delete the index-th node in the linked list, if the index is valid. */
        void deleteAtIndex(int index) { 
            if(index>num-1)
                return;
            Node *p =head;
            while (index--)
            { 
                p=p->next;
            }
            num--;
            p->next = p->next->next;
        }
        void print(){ 
            cout<<"list size = "<<num<<endl;
            Node*p =head->next;
            while (p)
            { 
                cout<<p->val<<" ";
                p=p->next;
            }
            cout<<endl;
            
        }
    };

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MTY3MjQwNA_size_16_color_FFFFFF_t_70 1]: /images/20221005/c45623a4386f4496be557d0dffd3abaa.png