init commit

Author: yuanyu90221

.github/workflows/go.yml

@@ -0,0 +1,26 @@
+name: Go
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  build_and_test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Setup Go
+        uses: actions/setup-go@v3
+        with:
+          go-version: 1.16
+      - name: Build
+        run: go build -v ./...
+      - name: Test
+        run: go test -v -cover ./...
+      - name: BenchmarkTest
+        run: go test -benchmem -run=none -bench ^BenchmarkTest sol/sol

.gitignore

@@ -0,0 +1,21 @@
+# If you prefer the allow list template instead of the deny list, see community template:
+# https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
+#
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/
+
+# Go workspace file
+go.work

.gitlab-ci.yml

@@ -0,0 +1,9 @@
+stages:
+  - test
+build and test:
+  image: golang:1.16
+  stage: test
+  script:
+    - go build -v ./...
+    - go test -v -cover ./...
+    - go test -benchmem -run=none ^BenchmarkTest sol/sol

.husky/pre-commit

@@ -0,0 +1,2 @@
+#!/bin/bash
+go test -v -cover ./...

README.md

@@ -0,0 +1,120 @@
+# golang_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
+```go
+package sol
+
+func isPalindrome(s string) bool {
+	lp, rp := 0, len(s)-1
+	var isAlphaBet = func(c byte) bool {
+		if ('a' <= c && 'z' >= c) || ('A' <= c && 'Z' >= c) {
+			return true
+		}
+		return false
+	}
+	var toLower = func(c byte) byte {
+		if 'A' <= c && 'Z' >= c {
+			return (c - 'A') + 'a'
+		}
+		return c
+	}
+	for lp <= rp {
+		if !isAlphaBet(s[lp]) {
+			lp++
+			continue
+		}
+		if !isAlphaBet(s[rp]) {
+			rp--
+			continue
+		}
+		if toLower(s[rp]) != toLower(s[lp]) {
+			return false
+		}
+		rp--
+		lp++
+	}
+	return true
+}
+```
+
+## 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

go.mod

@@ -0,0 +1,3 @@
+module sol
+
+go 1.16

sol/solution.go

@@ -0,0 +1,33 @@
+package sol
+
+func isPalindrome(s string) bool {
+	lp, rp := 0, len(s)-1
+	var isAlphaBet = func(c byte) bool {
+		if ('a' <= c && 'z' >= c) || ('A' <= c && 'Z' >= c) {
+			return true
+		}
+		return false
+	}
+	var toLower = func(c byte) byte {
+		if 'A' <= c && 'Z' >= c {
+			return (c - 'A') + 'a'
+		}
+		return c
+	}
+	for lp <= rp {
+		if !isAlphaBet(s[lp]) {
+			lp++
+			continue
+		}
+		if !isAlphaBet(s[rp]) {
+			rp--
+			continue
+		}
+		if toLower(s[rp]) != toLower(s[lp]) {
+			return false
+		}
+		rp--
+		lp++
+	}
+	return true
+}

sol/solution_test.go

@@ -0,0 +1,43 @@
+package sol
+
+import "testing"
+
+func BenchmarkTest(b *testing.B) {
+	s := "A man, a plan, a canal: Panama"
+	for idx := 0; idx < b.N; idx++ {
+		isPalindrome(s)
+	}
+}
+func Test_isPalindrome(t *testing.T) {
+	type args struct {
+		s string
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			name: "A man, a plan, a canal: Panama",
+			args: args{s: "A man, a plan, a canal: Panama"},
+			want: true,
+		},
+		{
+			name: "race a car",
+			args: args{s: "race a car"},
+			want: false,
+		},
+		{
+			name: " ",
+			args: args{s: " "},
+			want: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := isPalindrome(tt.args.s); got != tt.want {
+				t.Errorf("isPalindrome() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}