LeetCode解題(20200626)

面試題 02.01. 移除重複節點

/**
 * Copyright (C), 2018-2020
 * FileName: removeDuplicateNodes0201
 * Author:   xjl
 * Date:     2020/6/26 20:10
 * Description: 編寫代碼，移除未排序鏈表中的重複節點。保留最開始出現的節點。
 */
package LinkList;

import org.junit.Test;

import java.util.ArrayList;

public class removeDuplicateNodes0201 {

    public class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

    public ListNode removeDuplicateNodes1(ListNode head) {
        ArrayList<Integer> list = new ArrayList<>();
        ListNode pre = head;
        while (pre != null) {
            if (!list.contains(pre.val)) {
                list.add(pre.val);
            }
            pre = pre.next;
        }
        ListNode res = new ListNode(0);
        ListNode pre1=res;
        for (int V : list) {
            pre1.next = new ListNode(V);
            pre1 = pre1.next;
        }
        return res.next;
    }

    @Test
    public void test() {
        ListNode s1 = new ListNode(1);
        ListNode s2 = new ListNode(2);
        ListNode s3 = new ListNode(3);
        ListNode s4 = new ListNode(3);
        ListNode s5 = new ListNode(2);
        ListNode s6 = new ListNode(1);

        s1.next = s2;
        s2.next = s3;
        s3.next = s4;
        s4.next = s5;
        s5.next = s6;

        ListNode listNode = removeDuplicateNodes1(s1);
        while (listNode != null) {
            System.out.println(listNode.val);
            listNode = listNode.next;
        }
    }
}

刪除鏈表中相鄰的重複的元素

//刪除連續的重複的元素
    public ListNode removeDuplicateNodes(ListNode head) {
        ListNode node = new ListNode(0);
        node.next = head;

        ListNode curr = node;
        ListNode pre = head;

        curr.next = pre;

        while (pre.next != null) {
            if (pre.val == pre.next.val) {
                curr.next = pre.next;
                pre = pre.next;
                continue;
            }
            curr = curr.next;
            pre = pre.next;
        }
        return node.next;
    }

82. 刪除排序鏈表中的重複元素 II

class Solution {
    public ListNode deleteDuplicates(ListNode head) {
         ListNode node = new ListNode(0);
        node.next = head;
        ListNode pre = node;
        ListNode curr = head;
        while (curr != null) {
            if (curr.next != null && curr.val == curr.next.val) {
                while (curr.next != null && curr.val == curr.next.val) {
                    curr = curr.next;
                }
                curr = curr.next;
                pre.next = curr;
            } else {
                pre = pre.next;
                curr = curr.next;
            }
        }
        return node.next;
    }
}