Go学习笔记06-内建容器

Go学习笔记06-内建容器

Go语言

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数组

定义数组：

1. //这样定义数组编译器自动初始化每个元素为0 

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2. var arr1 [5]int 

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3.  

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4. //这样定义数组需要手动初始化数组 

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5. arr2 := [3]int{1, 3, 5} 

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6.  

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7. //这样可以让编译器自动计算数组长度 

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8. arr3 := [...]int{2, 4, 6, 8, 10} 

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9.  

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10. //定义二维数组 

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11. var grid [4][5]bool 

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·数量写在类型前面

遍历数组可用 for 循环语句，如：

1. //用len()函数获取数组长度 

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2. for i := 0;i < len(arr3); i++{ 

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3. fmt.Println(arr3[i]) 

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4. } 

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可以用range关键字获取数组的下标和值

1. //用 range 关键字获取数组的下标和值 

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2. for i, v := range arr3{ 

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3. //i为数组下标，v为值 

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4. fmt.Println(i, v) 

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5. } 

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6.  

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7. //只获取数值，下标值用 _ 代替 

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8. for _, v := range arr3{ 

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9. fmt.Println(v) 

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10. } 

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Go语言中数组是值类型

• [10]int和[20]int被视为不同的类型
• 函数调用时会拷贝数组
• Go语言中一般不直接使用数组

*切片(Slice)

定义一个数组 arr := […]int{0, 1, 2, 3, 4, 5, 6, 7}
那么 s := arr[2:6]就叫做数组arr的一个切片，其值为[2, 3, 4, 5]。

1. arr := [...]int{0, 1, 2, 3, 4, 5, 6, 7} 

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2.  

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3. //获取数组arr下标从2~5的元素，不包括下标为6的元素 

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4. fmt.Println("arr[2:6] =", arr[2:6]) 

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5. //获取从第一个元素到下标为5的元素 

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6. fmt.Println("arr[:6] =", arr[:6]) 

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7. //获取从下标为2的元素及其后所有的元素 

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8. fmt.Println("arr[2:] =", arr[2:]) 

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9. //获取整个数组的元素 

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10. fmt.Println("arr[:] =", arr[:]) 

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slice即切片不是值类型，切片是底层数组的一个视图(view)，对切片做的变更会影响到原数组。

切片可以再对其进行reslice操作。

切片的扩展

Slice的操作

Slice添加元素

1. arr := [...]int{0, 1, 2, 3, 4, 5, 6, 7} 

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2. //s1 = [2, 3, 4, 5] 

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3. s1 := arr[2:6] 

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4. //s2 = [5, 6] 

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5. s2 := s1[3:5] 

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6. //s3 = [5, 6, 10] 

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7. s3 := append(s2, 10) 

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8. //s4 = [5, 6, 10, 11] 

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9. s4 := append(s3, 11) 

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10. //s5 = [5, 6, 10, 11, 12] 

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11. s5 := append(s4, 12) 

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12.  

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13. //s4, s5是不同的数组的视图 

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• 添加元素时如果超越cap，系统会重新分配一个更大的底层数组
• 由于是值传递，必须接收append的返回值

创建Slice

1. //未初始化的Slice缺省值是 nil 

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2. var s []int 

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3.  

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4. //用make创建Slice，slice长度为6 

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5. s2 := make([]int, 6) 

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6. //用make创建Slice，slice长度为10，底层数组长度为32 

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7. s3 := make([]int, 10, 32) 

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复制Slice

1. //复制s1，并存储到s2中 

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2. copy(s2, s1) 

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Map

创建map

1. //创建map，m := map[Key_Type]Value_Type 

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2. m := map[string]string{ 

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3. "name": "Bob", 

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4. "course": "golang", 

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5. "site": "imooc", 

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6. "quality": "not bad" 

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7. } 

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8.  

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9. //用make创建map，缺省值为 empty map 

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10. m2 := make(map[string]int) 

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11.  

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12. //这样创建map，缺省值为nil 

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13. var m3 := map[string]int 

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遍历Map

1. //map的遍历同数组遍历操作 

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2. for k, v := range m{ 

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3. fmt.Println(k, v) 

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4. } 

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获取元素

1. courseName := m["course"] 

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2.  

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3. //用此方法可以判断map中是否含有key为cause的值 

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4. if causeName, isOk := m["cause"]; isOk{ 

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5. fmt.Println(causeName) 

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6. }else { 

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7. fmt.Println("Key does not exisit.") 

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8. } 

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删除元素

1. //用delete删除map元素 

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2. delete(m, "name") 

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map小结

map示例

题干：寻找最长不含有重复字符的子串的长度
如：abcabcbb -> abc
bbb -> b
pwwkew -> wke

1. package main 

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2.  

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3. import "fmt" 

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4.  

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5. func lengthOfNoneRepeatSubStr(s string) int{ 

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6. last := make(map[byte]int) 

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7. start := 0 

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8. maxLength := 0 

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9.  

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10. for i, ch := range []byte(s){ 

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11. if lastI, isOk := last[ch]; isOk && lastI >= start { 

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12. start = lastI + 1 

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13. } 

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14. if i - start + 1 > maxLength{ 

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15. maxLength = i - start + 1 

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16. } 

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17. last[ch] = i 

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18. } 

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19.  

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20. return maxLength 

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21. } 

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22.  

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23. func main() { 

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24. fmt.Println(lengthOfNoneRepeatSubStr("abcabcbb")) 

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25. fmt.Println(lengthOfNoneRepeatSubStr("kkkkkkkkk")) 

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26. fmt.Println(lengthOfNoneRepeatSubStr("pwwkew")) 

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27. fmt.Println(lengthOfNoneRepeatSubStr("0123456789")) 

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28. } 

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字符处理

在Go语言中，rune相当于char类型

1. package main 

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2.  

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3. import "fmt" 

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4.  

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5. func main(){ 

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6. s := "Yes青青子衿悠悠我心" 

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7. for _, b := range []byte(s){ 

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8. fmt.Printf("%X ", b) 

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9. } 

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10.  

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11. for i, ch := range s{ 

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12. fmt.Printf("(%d, %X) ", i, ch) 

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13. } 

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14.  

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15. fmt.Println() 

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16. } 

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• 使用utf8.RuneCountInString获取字符数量
• 使用len获取字节长度
• 使用[]byte获取字节

寻找最长不含有重复字符的子串的长度支持中文字符版本

1. package main 

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2.  

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3. import "fmt" 

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4.  

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5. func lengthOfNoneRepeatSubStr(s string) int{ 

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6. last := make(map[rune]int) 

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7. start := 0 

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8. maxLength := 0 

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9.  

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10. for i, ch := range []rune(s){ 

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11. if lastI, isOk := last[ch]; isOk && lastI >= start { 

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12. start = lastI + 1 

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13. } 

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14. if i - start + 1 > maxLength{ 

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15. maxLength = i - start + 1 

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16. } 

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17. last[ch] = i 

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18. } 

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19.  

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20. return maxLength 

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21. } 

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22.  

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23. func main() { 

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24. fmt.Println(lengthOfNoneRepeatSubStr("abcabcbb")) 

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25. fmt.Println(lengthOfNoneRepeatSubStr("kkkkkkkkk")) 

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26. fmt.Println(lengthOfNoneRepeatSubStr("pwwkew")) 

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27. fmt.Println(lengthOfNoneRepeatSubStr("0123456789")) 

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28. } 

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有关字符的操作在包 strings 中。