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Dummy????

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Dummy?????

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class ListNode {    public int val;    public ListNode next;    public ListNode(int value) {        val = value;    }}

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  ??????next?????null?

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public class LinkedList {    private ListNode dummy;    public LinkedList() {        dummy = new ListNode(-1);    }}

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  ?????dummy??????????????????

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1. ????

public void add(int location, int val) {    ListNode pre = dummy;    for (int i = 0; i < location; i++) {        pre = pre.next;    }    ListNode node = new ListNode(val);    node.next = pre.next;    pre.next = node;}

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  ???0?????????????????????

2. ????

public void remove(int location) {    ListNode pre = dummy;    for (int i = 0; i < location; i++) {        pre = pre.next;    }    pre.next = pre.next.next;}

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  ???????????????next????????

3. ????

public int get(int location) {    ListNode cur = dummy.next;    for (int i = 0; i < location; i++) {        cur = cur.next;    }    return cur.val;}

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4. ????

public boolean contain(int val) {    ListNode cur = dummy.next;    while (cur != null) {        if (cur.val == val) {            return true;        }        cur = cur.next;    }    return false;}

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  ?dummy??????????????????????????

5. ????

public void print() {    ListNode cur = dummy.next;    while (cur != null) {        System.out.print(cur.val + "->");        cur = cur.next;    }    System.out.println("null");}

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  ????????????null????????

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public static void main(String[] args) {    LinkedList list = new LinkedList();    list.add(0, 10);    list.add(1, 20);    list.add(2, 40);    list.remove(1);    list.print();    System.out.println(list.get(0));    System.out.println(list.get(1));    System.out.println(list.contain(50));    System.out.println(list.contain(40));}

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ArrayList?LinkedList???????

LeetCode????

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• Solution???

  LeetCode????Solution??????????????????

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