public class MyLinkedList { static class ListNode { int val; ListNode next; public ListNode(int val){ this.val = val; } } ListNode head;// 头结点 ListNode tail;// 尾结点 int size; public MyLinkedList(){ head = null; tail = null; size = 0; } // 插入方法 public void insert(int position, int number){ if(position > size){ return; } ListNode newNode = new ListNode(number); // 要插入的地位是0（即为头部） // case 1 : 头部插入 if(position == 0){ newNode.next = head; head = newNode; // 判断尾结点是不是null， 如果是null阐明这是插入的第一个元素 if(tail == null){ tail = newNode; } size++; } // case 2 : 尾部插入 else if(position == size){ this.append(number); } // case 3 : 两头插入 else { // 找到插入地位之前的节点 ListNode prev = head; for (int i = 0; i < position - 1; i++) { prev = prev.next; } ListNode next = prev.next; newNode.next = next; prev.next = newNode; size++; } } public void append(int number){ ListNode newNode = new ListNode(number); if(tail == null){ tail = newNode; } else { tail.next = newNode; tail = newNode; } size++; } // 删除 public void delete(int number){ // 删除头结点 if(head != null && head.val == number){ head = head.next; size--; // 如果size==0 阐明只有一个元素 if(size == 0) { tail = head; } } else { ListNode prev = head; ListNode current = head; while(prev != null && current != null){ if(current.val == number){ if(current == tail){ tail = prev; } prev.next = current.next; size--; return; } prev = current; current = current.next; } } } // 查找 返回地位 public int search(int number){ ListNode current = head; for (int i = 0; current != null; i++) { if(current.val == number){ return i; } current = current.next; } return -1; } // 批改 public int update(int oldValue, int newValue){ ListNode current = head; for (int i = 0; current != null; i++) { if(current.val == oldValue){ current.val = newValue; return i; } current = current.next; } return -1; } public static void main(String[] args) { }}