꾸준함이 실력입니다.

• LeetCode : 344. Reverse String

  2020-11-11

  goodGid

  LeetCode
  • (Easy) Reverse String
    • Problem
    • Example
    • Code (20. 11. 11) (x)

  (Easy) Reverse String

  Problem

  Write a function that reverses a string. The input string is given as an array of characters char[].
  Do not allocate extra space for another array, 
  you must do this by modifying the input array in-place with O(1) extra memory.
  You may assume all the characters consist of printable ascii characters.
  

  ---

  Example

  Input: ["h","e","l","l","o"]
  Output: ["o","l","l","e","h"]
  

  ---

  Code (20. 11. 11) (x)

  public void reverseString(char[] s) {
      int length = s.length;
      char[] ans = new char[length];
  
      for (int i = 0; i < length; i++) {
          ans[i] = s[length - 1 - i];
      }
  
      for (int i = 0; i < length; i++) {
          s[i] = ans[i];
      }
  }
  

  • 막 풀어도 될까 했는데 풀리는구나.

    그래도 좋은 코드 참고하자.

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• LeetCode : 104. Maximum Depth of Binary Tree

  2020-11-11

  goodGid

  LeetCode
  • Maximum Depth of Binary Tree
    • Problem
    • Example
    • Code (20. 11. 11)
    • Code (21. 07. 14)
    • Code (21. 09. 19) (x)
  • Reference

  Maximum Depth of Binary Tree

  Problem

  Given a binary tree, find its maximum depth.
  The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
  Note: A leaf is a node with no children.
  

  ---

  Example

  Given binary tree [3,9,20,null,null,15,7],
      3
     / \
    9  20
      /  \
     15   7
  

  ---

  Code (20. 11. 11)

  public int maxDepth(TreeNode root) {
      return find(0, root);
  }
  
  public int find(int depth, TreeNode node) {
      if (node == null) {
          return depth;
      }
      return Math.max(find(depth + 1, node.left), find(depth + 1, node.right));
  }
  

  • 머리 아팠다.

    오랜만에 재귀로 푸려니까 너무 어려웠다.

  ---

  Code (21. 07. 14)

  class Solution {
  
      public int maxDepth(TreeNode root) {
          if (root == null) {
              return 0;
          }
  
          return getMaxDepth(root, 1);
      }
  
      public int getMaxDepth(TreeNode node, int ans) {
          if (node == null) {
              return ans;
          }
  
          int leftMaxDepth = 0;
          int rightMaxDepth = 0;
  
          if (node.left != null) {
              leftMaxDepth = getMaxDepth(node.left, ans + 1);
              System.out.println("leftMaxDepth : " + leftMaxDepth);
          }
  
          if (node.right != null) {
              rightMaxDepth = getMaxDepth(node.right, ans + 1);
              System.out.println("rightMaxDepth : " + rightMaxDepth);
          }
  
          ans = Math.max(ans, Math.max(leftMaxDepth, rightMaxDepth));
  
          return ans;
      }
  }
  

  • LeetCode 웹 IDE에서 바로 풀었다.

    풀 수 있을까? 했는데 두드려보니 풀렸다.

  ---

  Code (21. 09. 19) (x)

  class Solution {
      public int maxDepth(TreeNode root) {
          return go(root,0,0);
      }
      
      private int go(TreeNode node, int depth, int ans) {
          if (node == null) {
              return depth;
          }
          
          ans = Math.max(ans, go(node.left, depth+1, ans));
          ans = Math.max(ans, go(node.right, depth+1, ans));
          
          return ans;
      }
  }
  

  • 다시 풀 필요 X

  ---

  Reference

  • 104. Maximum Depth of Binary Tree
  Read All

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• Google Adsense : $100를 돌파하다.

  2020-11-10

  goodGid

  E.T.C
  • Google Adsense
    • $100 달성

  Google Adsense

  • Google Adsense의 수익금 $100를 돌파했다.

  ---

  $100 달성

  • Google Adsense Home에 들어가니

    다음과 같은 화면이 나를 반겼다.

    바로 업데이트 버튼을 눌렀다.

  

  • 업데이트 버튼을 누르면 다음과 같은 화면이 보인다.

  

  • Google Adsense 가입 시

    결제 수단을 설정하지 않았기 때문에 설정을 해준다.

  

  • 정상적으로 등록되었고 이제 저 계좌로 돈이 들어오는 걸 기다리면 된다.

  

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• Spring Boot SQL Option : 'show_sql' Option Deep 하게 알아보기

  2020-11-09

  goodGid

  SpringBoot
  • Prologue

  Prologue

  • 이 글을 시작하기에 앞서

    해당 글에서 사용하는 SQL Option을 모르겠다면

    Spring Boot SQL Option 알아보기 글을 참고하자.

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  ---

• LeetCode : 7. Reverse Integer

  2020-11-09

  goodGid

  LeetCode
  • (Easy) Reverse Integer
    • Problem
    • Example
    • Code (20. 11. 08)
    • Feed Back

  (Easy) Reverse Integer

  Problem

  Given a 32-bit signed integer, reverse digits of an integer.
  
  Note:
  Assume we are dealing with an environment that could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. 
  For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
  

  ---

  Example

  Input: x = 123
  Output: 321
  

  ---

  Code (20. 11. 08)

  public int reverse(int x) {
      if (x == 0) {
          return 0;
      }
  
      while (true) {
          if (x % 10 == 0) {
              x /= 10;
          } else {
              break;
          }
      }
  
      StringBuilder answer = new StringBuilder();
      if (x < 0) {
          answer.append("-");
          x *= -1;
      }
  
      while (x != 0) {
          answer.append(x % 10);
          x /= 10;
      }
  
      int ans;
      try {
          ans = Integer.parseInt(answer.toString());
      } catch (Exception e){
          return 0;
      }
      return ans;
  }
  

  ---

  Feed Back

  Case 1

  class Solution {
      public int reverse(int x) {
          long num = 0;
          while (x != 0) {
              num = num * 10 + x % 10;
              x = x / 10;
          }
  
          if (num != (int) num) {
              return 0;
          }
          return (int) num;
      }
  }
  

  • long으로 계산하고 int로 변환한다는 아이디어가 좋았다.

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• Spring Boot SQL Option 알아보기 :: show_sql, format_sql, use_sql_comments, org.hibernate.type.descriptor.sql

  2020-11-08

  goodGid

  SpringBoot
  • SQL Option
    • SQL 보기

  SQL Option

  SQL 보기

  • Hibernate가 DB에 날리는 모든 Query를 보여준다.

  • 해당 옵션과 관련해서는 반드시 알아야 할 부분이 있다.

    그 부분에 대해서는 Spring Boot SQL Option : ‘show_sql’ Option Deep 하게 알아보기 글을 참고하자.

  application.yml

  spring:
    jpa:
      properties:
        hibernate:
          show_sql: true
  

  application.properties

  spring.jpa.properties.hibernate.show_sql = true
  

  Output

  Hibernate: select testentity0_.id as id1_8_0_ from test_entity testentity0_ where testentity0_.id=?
  Hibernate: insert into test_entity (id) values (?)
  

  Read All

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