链表复习（二）

删除链表函数：

void delete_node(int index){
       if(head==NULL){
           return;
       }
       Node* current_node=head;
       int count=0;
       if(index==0){
           head=head->next;
           delete current_node;
           return;
       }

       while(current_node->next!=NULL&&count<index-1){
           current_node=current_node->next;
           count++;
       }
       if(count==index-1&&current_node->next!=NULL){
           Node* delete_node=current_node->next;
           current_node->next=delete_node->next;
           delete delete_node;
           
       }
   }

反转链表函数：

void reverse(){
        if(head==NULL){
            return;        
        }
        Node *next_node,*current_node;
        current_node=head->next;
        head->next=NULL;
        while(current_node!=NULL){
            next_node=current_node->next;
            current_node->next=head;
            head=current_node;
            current_node=next_node;
        }
    }

循环链表：

注意head代表头结点，也代表尾节点

void insert(Node *node, int index) {
       if (head == NULL) {
           head = node;   //当只有一个节点时head的next就是head自己
           head->next = head;
           return;
       }
       if (index == 0) {
           node->next = head->next; //在head后插入
           head->next = node;
           return;
       }
       Node *current_node = head->next;
       int count = 0;
       while (current_node != head && count < index – 1) {
           current_node = current_node->next;
           count++;
       }
       if (count == index – 1) {
           node->next = current_node->next;
           current_node->next = node;
       }
       if (node == head->next) {//如果把node插在了head后面则将head设置为node
           head = node;
       }
   }