init comit

Author: yuanyu90221

.github/workflows/java.yml

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+name: Java
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Setup JDK 11
+        uses: actions/setup-java@v3
+        with:
+          distribution: 'adopt'
+          java-version: '11'
+      - name: Grant execution permission for gradlew
+        run: chmod +x gradlew
+      - name: Cache Gradle packages
+        uses: actions/cache@v3
+        with:
+          path: ~/.gradle/caches
+          key: ${{ runner.os }}-gradle-${{ github.event.repository.name }}-${{ hashFiles('**/*.gradle')}}
+          restore-keys: ${{ runner.os }}-gradle-${{ github.event.repository.name }}
+      - name: Build with Gradlew
+        run: ./gradlew build
+      - name: Test with Gradlew
+        run: ./gradlew :test --tests "SolutionTest"

.gitignore

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+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store

.husky/pre-commit

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+#!/bin/bash
+./gradlew :test --tests "SolutionTest"

.idea/gradle.xml

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+# java_valid_palindrome
+
+A phrase is a **palindrome** if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
+
+Given a string `s`, return `true` *if it is a **palindrome**, or* `false` *otherwise*.
+
+## Examples
+
+**Example 1:**
+
+```
+Input: s = "A man, a plan, a canal: Panama"
+Output: true
+Explanation: "amanaplanacanalpanama" is a palindrome.
+
+```
+
+**Example 2:**
+
+```
+Input: s = "race a car"
+Output: false
+Explanation: "raceacar" is not a palindrome.
+
+```
+
+**Example 3:**
+
+```
+Input: s = " "
+Output: true
+Explanation: s is an empty string "" after removing non-alphanumeric characters.
+Since an empty string reads the same forward and backward, it is a palindrome.
+```
+
+**Constraints:**
+
+- `1 <= s.length <= 2 * 105`
+- `s` consists only of printable ASCII characters.
+
+## 解析
+
+給定一個字串 s ,
+
+假設經過一個運算只看是英文字母的字元，且把所有大寫英文字元轉成小寫後變成 s’
+
+要求寫一個演算法判斷 s 在經過以上轉換後是否是回文字串
+
+一個字串 s 如果是回文， 代表 i = 0..(n/2-1)
+
+s[i] = s[n-1-i], where n = len(s)
+
+由以上定義可以發現透過給定 2 個指標 一個從字串最前面 一個從字串最後面
+
+當兩個指標位置不同時做以下比較
+
+每次當遇到兩個字元相同時，兩個指標共同推進一個單位往下一個可以比較的字元去比較
+
+遇到兩個字元不同時，則代表不是回文 回傳 false
+
+特別要注意的是當其中一個指標遇到不是非英文字元，則需要直接把指標往下一個位置移動 
+
+然後往一下個開始指標開始比較
+
+假設直到最後一個指標都相同則代表是回文 所以回傳 true
+
+演算法詳細如下圖
+
+![](https://i.imgur.com/BxTUXpO.png)
+
+## 程式碼
+```java
+public class Solution {
+  public boolean isPalindrome(String s) {
+    int lp = 0, rp = s.length() - 1;
+    while(lp <= rp) {
+      if (!isAlphabet(s.charAt(lp))) {
+        lp++;
+        continue;
+      }
+      if (!isAlphabet(s.charAt(rp))) {
+        rp--;
+        continue;
+      }
+      if (toLower(s.charAt(rp)) != toLower(s.charAt(lp)) ) {
+        return false;
+      }
+      lp++;
+      rp--;
+    }
+    return true;
+  }
+  private boolean isAlphabet(char c) {
+    if (('a' <= c && c < 'z') || ('A' <= c && c < 'Z') || ('0' <= c && c <= '9')) {
+      return true;
+    }
+    return false;
+  }
+  private char toLower(char c) {
+    if ('A' <= c && c < 'Z') {
+      return (char)(c - 'A' + 'a');
+    }
+    return c;
+  }
+}
+
+```
+
+## 困難點
+
+1. 從 palindrome 定義思考出透過左右指標同時逼近來檢查
+
+## Solve Point
+
+- [x]  初始化 lp = 0, rp = len(s) -1
+- [x]  for lp ≤ rp 做以下運算
+- [x]  當 s[lp] 不在 ‘a’,’z’ 之間 且不在 ‘A’ ,‘Z’之間, 更新 lp += 1 continue
+- [x]  當 s[rp] 不在 ‘a’,’z’ 之間 且不在 ‘A’ ,‘Z’之間, 更新 rp -= 1 continue
+- [x]  當 toLower(s[rp]) ≠ toLower(s[lp]) , 回傳 false
+- [x]  rp—; lp++
+- [x]  回傳 true

.idea/misc.xml

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+plugins {
+    id 'java'
+}
+
+group 'org.example'
+version '1.0-SNAPSHOT'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
+}
+
+test {
+    useJUnitPlatform()
+}

.idea/vcs.xml

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.4-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists