《LeetCode力扣练习》代码随想录——链表（设计链表---Java）

《LeetCode力扣练习》代码随想录——链表（设计链表—Java）

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刷题思路来源于 代码随想录

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707. 设计链表

• 虚拟头结点

  class MyLinkedList {
  
      class ListNode{
  
          int val;
          ListNode next;
  
          ListNode(){
  
          }
  
          ListNode(int val){
              this.val=val;
          }
  
          ListNode(int val,ListNode next){
              this.val=val;
              this.next=next;
          }
  
      }
  
      private int size;
      private ListNode dummyHead;
  
      public MyLinkedList() {
  
          this.size=0;
          this.dummyHead=new ListNode(0,null);
  
      }
      
      public int get(int index) {
  
          if(this.size==0||index>=this.size){
              return -1;
          }
  
          ListNode current=this.dummyHead.next;
  
          while(index>0){
              current=current.next;
              index--;
          }
  
          return current.val;
  
      }
      
      public void addAtHead(int val) {
  
          addAtIndex(0,val);
          return;
  
      }
      
      public void addAtTail(int val) {
  
          addAtIndex(this.size,val);
          return;
  
      }
      
      public void addAtIndex(int index, int val) {
  
          if(index>this.size){
              return;
          }
  
          ListNode current=this.dummyHead;
  
          while(index>0){
              current=current.next;
              index--;
          }
  
          ListNode newNode=new ListNode(val,current.next);
          current.next=newNode;
          this.size++;
  
          return;
  
      }
      
      public void deleteAtIndex(int index) {
  
          if(this.size==0||index>=this.size){
              return;
          }
  
          ListNode current=this.dummyHead;
  
          while(index>0){
              current=current.next;
              index--;
          }
  
          current.next=current.next.next;
          this.size--;
  
          return;
  
      }
  }
  
  /**
   * Your MyLinkedList object will be instantiated and called as such:
   * MyLinkedList obj = new MyLinkedList();
   * int param_1 = obj.get(index);
   * obj.addAtHead(val);
   * obj.addAtTail(val);
   * obj.addAtIndex(index,val);
   * obj.deleteAtIndex(index);
   */
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