public class SinglyListNode {
int val;
SinglyListNode next;
SinglyListNode() {
}
SinglyListNode(int x) {
this.val = x;
}
}
/*執行用時：
12 ms
, 在所有 Java 提交中擊敗了
66.93%
的用戶
內存消耗：
39.5 MB
, 在所有 Java 提交中擊敗了
5.06%
的用戶
*/
class MyLinkedList {
int size; // 0 -- n
//SinglyListNode head = new SinglyListNode(); // 此種寫法錯誤，鏈表遍歷時最后會輸出0
SinglyListNode head = null;
/** Initialize your data structure here. */
public MyLinkedList() {
}
/*public int length() {
int length = 0;
SinglyListNode p = head;
while (p != null) {
length ++;
p = p.next;
}
return length;
}*/
/** Get the value of the index-th node in the linked list. If the index is invalid, return -1. */
public int get(int index) {
if (index < 0 || index >= size) {
return -1;
}
SinglyListNode p;
p = head;
if (index != 0) {
for (int i = 0; i < index; i++) {
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. */
public void addAtHead(int val) {
SinglyListNode listNode = new SinglyListNode(val); // 創建加入的節結點
if (head != null) {
listNode.next = head;// 新節點的指針域指向當前鏈表的頭節點
}
head = listNode; // 將插入的節點作為新的頭節點
size ++;
}
/** Append a node of value val to the last element of the linked list. */
public void addAtTail(int val) {
SinglyListNode listNode = new SinglyListNode(val);
if(head == null) {
head = listNode;
size ++;
// listNode.next = null; // 冗余
return;
}
SinglyListNode p = head;
/*while (p != null) {
if (p.next == null) {
p.next = listNode;
listNode.next = null;
p = null; //循環終止條件
}else {
p = p.next;
}
}*/
while (p.next != null) {
p = p.next; // 遍歷到尾節點位置
}
p.next =listNode;
size ++;
}
/** 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. */
public void addAtIndex(int index, int val) {
if (index == size) {
addAtTail(val);
return;
}
if (index <= 0) {
addAtHead(val);
return;
}
if (index > size - 1) {
return;
}
SinglyListNode listNode = new SinglyListNode(val);
SinglyListNode p = head;
// 遍歷到節點要插入位置的前一個位置
while (index - 1 > 0) {
p = p.next;
index --;
}
listNode.next = p.next;
p.next = listNode;
size ++;
}
/** Delete the index-th node in the linked list, if the index is valid. */
public void deleteAtIndex(int index) {
if (index < 0 || index >= size) {
return;
}
if (index == 0) {
head = head.next;
size --;
return;
}
SinglyListNode p = head;
SinglyListNode tempNode;
while (index - 1 > 0) {
p = p.next;
index --;
}
tempNode = p.next.next;
p.next = tempNode;
size --;
}
}
