设计链表

设计链表

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class Node {
    int val;
    Node next;
    Node(){}
    Node(int val){
        this.val = val;
    }
}
class MyLinkedList {
    int size; //存储节点个数
    Node head;

    public MyLinkedList() {
        size = 0;
        head = new Node(0);

    }
    
    public int get(int index) {
        if(index < 0 || index >= size)
            return -1;

        Node cur = head;
        for(int i=0;i<=index;i++){
            cur = cur.next;
        }

        return cur.val;
    }
    
    public void addAtHead(int val) {
        addAtIndex(0,val);
    }
    
    public void addAtTail(int val) {
        addAtIndex(size,val);
    }
    
    public void addAtIndex(int index, int val) {
        if(index >size)
            return;
        if(index < 0)
            index = 0;
        size++;
        Node cur = head;
        for(int i = 0 ;i<index;i++)
            cur = cur.next;

        Node node = new Node(val);
        node.next = cur.next;
        cur.next = node;
    }
    
    public void deleteAtIndex(int index) {
        if(index<0 || index >= size)
            return;
        Node cur = head;
        size--;
        for(int i = 0; i<index ;i++)
            cur = cur.next;
        
        cur.next = cur.next.next;

    }
}