Golang M 2023 4 topic

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topic

数组求和

package main

import "fmt"

func main() 
	var i [10]int = [10]int8, 3, 2, 9, 4, 6, 10, 0, 7, 11
	j := sumArray(i)
	fmt.Println(i)
	fmt.Println(j)


func sumArray(a [10]int) int 
	var sum int = 0
	// 第一种遍历方式
	for i := 0; i < len(a); i++ 
		sum = sum + a[i]
	
	// 第二种遍历方式
	// for _, v := range a 
	// 	sum = sum + v
	// 
	return sum


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
[8 3 2 9 4 6 10 0 7 11]
60
PS E:\\TEXT\\test_go\\one>

func main() 
	var b [10]int
	for i := 0; i < len(b); i++ 
		b[i] = i
	
	sum := sumArray(b)
	fmt.Printf("sum=%d", sum)
	// sum=45


package main

import (
	"fmt"
	"math/rand"
)

func main() 
	var b [10]int
	for i := 0; i < len(b); i++ 
		// 随机值
		b[i] = rand.Intn(1000)
	
	sum := sumArray(b)
	fmt.Printf("sum=%d", sum)
	// sum=45


func main() 
	// 初始化随机种子
	rand.Seed(time.Now().Unix())
	var b [10]int
	for i := 0; i < len(b); i++ 
		// 产出一个 0 到 999 的随机种子
		b[i] = rand.Intn(1000)
		// 产生一个 0 到 int 最大值的随机数
		// b[i] = rand.Int()
	
	sum := sumArray(b)
	fmt.Printf("sum=%d", sum)
	// sum=45

二维数组以及遍历

package main

import "fmt"

func main() 
	testArray()


func testArray() 
	a := [5]int3: 100, 4: 300
	for i := 0; i < len(a); i++ 
		fmt.Printf("a[%d]=%d\\n", i, a[i])
	


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
a[0]=0
a[1]=0
a[2]=0
a[3]=100
a[4]=300
PS E:\\TEXT\\test_go\\one>

package main

import "fmt"

func main() 
	testArray()


func testArray() 
	var a [3][2]int
	a[0][0] = 10
	a[0][1] = 20
	a[1][0] = 30
	a[1][1] = 40
	a[2][0] = 50
	a[2][1] = 60
	// fmt.Println(a) [[10 20] [30 40] [50 60]]

	for i := 0; i < 3; i++ 
		for j := 0; j < 2; j++ 
			fmt.Printf("%d ", a[i][j])
		
		fmt.Println()
	


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
10 20
30 40
50 60
PS E:\\TEXT\\test_go\\one>

第二种遍历方式

func testArray() 
	var a [3][2]int
	a[0][0] = 10
	a[0][1] = 20
	a[1][0] = 30
	a[1][1] = 40
	a[2][0] = 50
	a[2][1] = 60
	// fmt.Println(a) [[10 20] [30 40] [50 60]]

	for i, v := range a 
		for j, v2 := range v 
			fmt.Printf("(%d,%d)=%d ", i, j, v2)
		
		fmt.Println()
	


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
(0,0)=10 (0,1)=20
(1,0)=30 (1,1)=40
(2,0)=50 (2,1)=60
PS E:\\TEXT\\test_go\\one>

找出数组两个元素之和等于 8

找出数组中和为给给定值的两个元素的下标，比如数组：[1,3,5,8,7]，找出两个元素之和等于 8 的下标分别是（0,4）和（1,2）。

package main

import "fmt"

func main() 
	b := [...]int1, 3, 5, 8, 7
	TwoSum(b, 8)


func TwoSum(a [5]int, target int) 
	for i := 0; i < len(a); i++ 
		other := target - a[i]
		for j := i + 1; j < len(a); j++ 
			if a[j] == other 
				fmt.Printf("(%d,%d)\\n", i, j)

切片追加切片

package main

import "fmt"

func main() 
	testAppend()


func testAppend() 
	var a []int = []int1, 3, 4
	var b []int = []int4, 5, 6

	a = append(a, 23, 34, 45)
	fmt.Printf("a=%v\\n", a)

	a = append(a, b...)
	fmt.Printf("a=%v\\n", a)


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
a=[1 3 4 23 34 45]
a=[1 3 4 23 34 45 4 5 6]
PS E:\\TEXT\\test_go\\one>

切片传参

package main

import "fmt"

func main() 
	nos := []int8, 7, 6
	fmt.Println("slice before function call", nos)

	subtactOne(nos)
	// nos 修改生效了，说明切片是引用类型
	fmt.Println("slice after function call", nos)


func subtactOne(numbers []int) 
	for i := range numbers 
		numbers[i] -= 2
	


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
slice before function call [8 7 6]
slice after function call [6 5 4]
PS E:\\TEXT\\test_go\\one>

数组获取成切片

package main

import "fmt"

func main() 
	var a [10]int = [10]int1, 3, 3, 4, 5, 5, 8
	sum := sumArray(a[:])
	fmt.Println("sum:", sum)


func sumArray(a []int) int 
	var sum int = 0
	for _, v := range a 
		sum = sum + v
	
	return sum


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
sum: 29
PS E:\\TEXT\\test_go\\one>

make([]string, 5, 10)

package main

import "fmt"

func main() 
	var sa = make([]string, 5, 10)
	fmt.Println("a:", sa)
	for i := 0; i < 10; i++ 
		sa = append(sa, fmt.Sprintf("%v", i))
	
	fmt.Println("a:", sa)


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
a: [    ]
a: [     0 1 2 3 4 5 6 7 8 9]
PS E:\\TEXT\\test_go\\one>

sort 排序

正序 int、string、float64

package main

import (
	"fmt"
	"sort"
)

func main() 
	var a [6]int = [6]int5, 4, 3, 2, 1, 0
	sort.Ints(a[:])
	fmt.Println("a:", a)

	var b [5]string = [5]string"ac", "ec", "bc", "fa", "cc"
	sort.Strings(b[:])
	fmt.Println("b:", b)

	var c [5]float64 = [5]float6429.38, 22.32, 0.8, 88.8, 55.5
	sort.Float64s(c[:])
	fmt.Println("c:", c)



PS E:\\TEXT\\test_go\\one> go run .\\test1.go
a: [0 1 2 3 4 5]
b: [ac bc cc ec fa]
c: [0.8 22.32 29.38 55.5 88.8]
PS E:\\TEXT\\test_go\\one>

倒序转换 intTmp 为 IntSlice 类型

package main

import (
	"fmt"
	"sort"
)

func main() 
	intTmp := []int
		6, 3, 9, 8, 1, 2, 5, 7,
	

	//转换intTmp为IntSlice类型
	sort.Sort(sort.IntSlice(intTmp))
	fmt.Println(intTmp)
	//[1 2 3 5 6 7 8 9]

	sort.Sort(sort.Reverse(sort.IntSlice(intTmp)))
	fmt.Println(intTmp)
	//[9 8 7 6 5 3 2 1]

结构体切片排序

package main

import (
	"fmt"
	"sort"
)

type Person struct 
	Name string
	Age  int


func TestSortSlice() 
	people := []Person
		"Bob", 31,
		"John", 42,
		"Michael", 17,
		"Jenny", 26,
	

	// 稳定排序正序
	sort.SliceStable(people, func(i, j int) bool 
		return people[i].Age < people[j].Age
	)
	fmt.Println(people)

	// 稳定排序倒序
	sort.SliceStable(people, func(i, j int) bool 
		return people[i].Age > people[j].Age
	)
	fmt.Println(people)


func main() 
	TestSortSlice()


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
[Michael 17 Jenny 26 Bob 31 John 42]
[John 42 Bob 31 Jenny 26 Michael 17]
PS E:\\TEXT\\test_go\\one>

map 按切片按值排序

package main

import (
	"fmt"
	"sort"
)

func main() 
	//待排序队列
	var stuScore = map[string]int"ee": 20, "cc": 90, "ff": 70, "qq": 40, "aa": 79, "bb": 30

	//创建切片，遍历map的值
	var nums = []int
	for _, v := range stuScore 
		nums = append(nums, v)
	
	//对切片按值排序
	//sort.Ints(nums)
	sort.Sort(sort.Reverse(sort.IntSlice(nums)))
	fmt.Println(nums)

	for _, num := range nums 
		//遍历map的key和值，与切片中的元素做比对
		for k, v := range stuScore 
			if v == num 
				fmt.Println(k, v)
			
		
	


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
[90 79 70 40 30 20]
cc 90
aa 79
ff 70
qq 40
bb 30
ee 20
PS E:\\TEXT\\test_go\\one>

go 输出 26 个英文字母

func test1() 
	for i := 'A'; i <= 'Z'; i++ 
		fmt.Printf("%c", i)

指针传参

package main

import "fmt"

func change(val *int) 
	*val = 55


func main() 
	a := 58
	fmt.Println("value of a before function call is", a)
	b := &a
	change(b)
	fmt.Println("value of a after function call is", a)


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
value of a before function call is 58
value of a after function call is 55
PS E:\\TEXT\\test_go\\one>

make & new 的区别以及值拷贝和引用拷贝

make 用来分配引用类型的内存，比如 map、slice 以及 channel 。

new 用来分配除引用类型的所有其他类型的内存，比如 int 、数组等。

package main

import "fmt"

func main() 
	var a *int = new(int)
	*a = 100
	fmt.Printf("*a=%d\\n", *a)

	var b *[]int = new([]int)
	fmt.Printf("*b=%v\\n", *b)

	(*b) = make([]int, 5, 100)
	(*b)[0] = 100
	(*b)[1] = 200
	fmt.Printf("*b=%v\\n", *b)


PS E:\\TEXT\\test_go\\one> go run .\\test1.go
*a=100
*b=[]
*b=[100 200 0 0 0]
PS E:\\TEXT\\test_go\\one>

1 写一个程序，获取一个变量的地址，并打印到终端

package main

import "fmt"

func main() 
	var a int = 100
	fmt.Printf("addr:%p\\n", &a)
	// addr:0xc00000e0b8

2 写一个函数，传入一个 int 类型的指针，并在函数中修改所指向的值

package main

import "fmt"

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