logseq_notes/journals/2023_03_28.md

- Daily reflection [[Daily reflections]]
  collapsed:: true
  - What I've done
  - What I've thought #thoughts
    - 10:08
      - logseq 比 obsidian 好用，计笔记成本低，而且好用，便携。
  - Mood
    - 10:09
      - 平静且开心(lol)
-
- DONE [#C] 票在书包里
  SCHEDULED: <2023-03-30 Thu>
-
- Todos:
  - Personal
    - DONE 重新浸洗袜子和内裤
      SCHEDULED: <2023-03-28 Tue 13:00>
      :LOGBOOK:
      CLOCK: [2023-03-28 Tue 15:55:30]--[2023-03-28 Tue 15:55:31] => 00:00:01
      :END:
    - DONE 洗眼镜
      SCHEDULED: <2023-03-28 Tue 13:00>
      :LOGBOOK:
      CLOCK: [2023-03-28 Tue 18:07:51]--[2023-03-28 Tue 22:41:19] => 04:33:28
      :END:
    - DONE Anki card for cloud collection 还不如没事多翻下书
      SCHEDULED: <2023-04-01 Sat>
  - School
    - DONE 交选题
      :LOGBOOK:
      CLOCK: [2023-03-28 Tue 16:19:35]
      CLOCK: [2023-03-28 Tue 16:19:40]--[2023-03-28 Tue 18:51:31] => 02:31:51
      :END:
    - DONE [#A] 复习 java
      :LOGBOOK:
      CLOCK: [2023-03-28 Tue 20:03:20]--[2023-03-29 Wed 22:25:48] => 26:22:28
      :END:
      - DONE 做题
        :LOGBOOK:
        CLOCK: [2023-03-28 Tue 20:03:29]--[2023-03-29 Wed 11:11:16] => 15:07:47
        :END:
        - DONE 练习题
          :LOGBOOK:
          CLOCK: [2023-03-28 Tue 20:03:51]--[2023-03-28 Tue 20:39:32] => 00:35:41
          :END:
        - DONE 往年题
          :LOGBOOK:
          CLOCK: [2023-03-28 Tue 20:03:50]--[2023-03-28 Tue 22:41:14] => 02:37:24
          :END:
        - DONE Leetcode
          :LOGBOOK:
          CLOCK: [2023-03-29 Wed 11:19:02]
          CLOCK: [2023-03-29 Wed 11:19:04]--[2023-03-29 Wed 16:52:09] => 05:33:05
          :END:
      - DONE 看 ppt
        :LOGBOOK:
        CLOCK: [2023-03-28 Tue 20:03:30]--[2023-03-29 Wed 11:18:53] => 15:15:23
        :END:
-
- OJ problem notes
  - Name:
    - Contains Duplicate
  - Times:
    - Completion time: 14:31
    - Revisions:
  - Tags:
    - Data structures: #hash_table
    - Difficulty: #difficulty_easy
    - Platforms: #leetcode
  - Links:
    - [link to the problem](https://leetcode.com/problems/contains-duplicate/description/)
  - Problem:
    - Given an integer array `nums`, return `true` if any value appears **at least twice** in the array, and return `false` if every element is distinct.
  - Examples:
    - ```


      Example 1:

      Input: nums = [1,2,3,1]
      Output: true

      Example 2:

      Input: nums = [1,2,3,4]
      Output: false

      Example 3:

      Input: nums = [1,1,1,3,3,4,3,2,4,2]
      Output: true

      ```
  - Constraints:
    - `1 <= nums.length <= 105`
    - `-109 <= nums[i] <= 109`
  - Thoughts:
    - Very simple hash map problem
  - Solution:
    - ```java
      class Solution {
          public boolean containsDuplicate(int[] nums) {
              Set <Integer> set = new HashSet<Integer>();
              for (int i : nums) {
                  if (set.contains(i)) {
                      return true;
                  } else {
                      set.add(i);
                  }
              }

              return false;
          }
      }
      ```
  -
  -
-
- Java 练习题 1 #to_be_deleted
  collapsed:: true
  - Q1
    - `less than 10`
  - Q2
    - `greater than 10`
  - Q3
    - `yes`
  - Q4
    - ```
      zero
      one
      none
      ```
  - Q5
    - ```
      zero
      one
      none
      one
      none
      none
      ```
  - Q6
    - ```
      zero
      none
      one
      zero
      none
      none
      ```
  - Q7
    - ```java
      int sum;
      for (int i = 1; i <= 100; i++) {
        sum += i;
      }
      System.out.println(sum);
      ```
  - Q8
    - ```java
      for (int i = 1; i <= 3; i++) {
        for (int j = 1; j <= 3; j++) {
          System.out.print(i * j + " ");
        }
        System.out.println();
      }
      ```
  - Q9
    - ```
      9
      8
      true
      ```
  - Q10
    - ```java
      int sum = 0;
      for (int i = 1; i <= 99; i++) {
        if (i % 3 == 0) {
          sum += i;
        }
      }
      System.out.println(sum);
      ```
  - Q11 不想写
  - Q12
    - What does overloading mean?
    - What does overloading do?
-
- java 练习题 2 [qmplus](https://qmplus.qmul.ac.uk/course/view.php?id=21582#section-8) #to_be_deleted
  - Q1
    - no.1 : not a array
      no.2 : `int[] marks = new int[60]`
      no.3 : `{'a', 'b', 'c'}`
      no.4 : use ""
  - Q2
    - Compile error
  - Q3
    - `F[1]` is not initiated, it only has a null value
  - Q4
    - Array index out of bounds, f[2] is non-exist
  - Q5
    - compile error, local variable won't be initialized as default val
  - Q6
    - 36, 36.0
  - Q7
    - first one invalid
      - Reason: wrong parameters
    - third one invalid
      - Reason: double->int can't be done implicitly, you have to use type casts
  - Q8
    - ```
      vroom
      truck 1
      car 2
      ```
  - Q9
    - ```
      vroomT
      truck 1
      car 1
      ```
  - Q10
    - 634.5
    - Reason: calculated from left to right, all converted to String
  - Q11
    - F, only have access to package-private data
    - F, no multi-inheritance for classes
    - F, not required
    - F, you can have one
  - Q12
    - b
  - Q13
    - false
    - true
    - true (reference stored in string constant pool)
  - Q14
    collapsed:: true
    - 懒得写了
  - Q15
    collapsed:: true
    - 懒得写
  - Q16
    - What is a abstract class?
    - What is `toString` method?
    - What does polymorphism mean?