GO 切片(slice)相關語法

package main

import(
	"fmt"
)

func main() {
	var intArr [5]int = [...]int{1,2,3,4,5} //定義一個數組
	slice := intArr[2:4] //第二個(包含)下標到第四個下標(不包含)

	fmt.Println("slice = ", slice) //[3 4]
	fmt.Println("slice len = ", len(slice)) 
	fmt.Println("slice cap = ", cap(slice)) //切片的容量

	//經過make建立切片
	var makeSlice []int = make([]int, 2, 5)//第一個參數爲類型, 第二個參數爲len, 第三個爲cap
	fmt.Println("makeSlice = ", makeSlice) //數字類型(int, float)默認爲0, sting 爲'', bool爲false  和數組同樣
	fmt.Println("makeSlice len = ", len(makeSlice))
	fmt.Println("makeSlice cap = ", cap(makeSlice))

	//相似於make
	var mslice []string = []string{"zhangsan", "lisi", "wangwu", ""}
	mslice[3] = "ermazi"
	fmt.Println("mslice = ", mslice)
	fmt.Println("mslice len = ", len(mslice))
	fmt.Println("mslice cap = ", cap(mslice))

	//遍歷
	for i:=0; i < len(mslice); i++ {
		fmt.Printf("i = %v, v = %v\n", i, mslice[i])
	}

	for j,mv := range mslice {
		fmt.Printf("j = %v, mv = %v\n", j, mv)
	}

	//細節
	var testArr [5]int = [...]int{1,2,3,4,5}
	testSlice := testArr[0:len(testArr)] //取出數組裏面全部值 testArr[:]能夠簡寫成這樣
	startSlice := testArr[:4] //從0開始到第四個下標
	endSlice := testArr[2:] // 從2開始到結束

	testSlice2 := startSlice[1:3]//slice也能夠從slice種切,和數組的規則同樣
	testSlice[2] = 100 //slice 是引用，更改了值都會影響其它關聯的指向變量的值(testArr, starSlice對應的都改變了)

	fmt.Println("testArr = ", testArr)
	fmt.Println("testSlice = ", testSlice)
	fmt.Println("testSlice2 = ", testSlice2)
	fmt.Println("endSlice = ", endSlice) //testArr的值改變了;它也得改變

	//append,copy的使用
	var apSlice []int  = make([]int, 5, 10)
	apSlice = append(apSlice, 1, 2, 3, 4, 5) //追加元素
	fmt.Println("apSlice = ", apSlice) //[0 0 0 0 0 1 2 3 4 5]

	apSlice = append(apSlice, apSlice...)//也能夠追加一個slice
	fmt.Println("apSlice = ", apSlice) // [0 0 0 0 0 1 2 3 4 5 0 0 0 0 0 1 2 3 4 5]

	var coppySlice []string = []string{"zhangsan", "lisi", "wangwu"}
	var dslice []string = make([]string, 3, 3)
	copy(dslice, coppySlice) //把copySlice的值拷貝到dslice種
	fmt.Println("dslice = ", dslice)//[zhangsan lisi wangwu]

	var minSlice []string = make([]string, 1, 1)//只有一個長度
	copy(minSlice, coppySlice) //此時不會出現越界的錯誤,只是拷貝了一個值
	fmt.Println("minSlice = ", minSlice)//[zhangsan]

	//字符串底層是一個byte數組,因此能夠經過slice來操做
	str := "hello,gogogo"
	strSlice := str[2:6] //這個返回的string,感受應該是slice
	fmt.Printf("strSlice = %v, %T\n", strSlice, strSlice)

	arr := []byte(str) //string 轉換成byte切片
	fmt.Printf("arr = %v, %T\n", arr, arr)
	arr[0] = 'H'
	//arr[1] = '我' //中文會報錯
	str = string(arr[:]) //[]byte切片轉換成字符串
	fmt.Println(str) //Hello,gogogo

	//經過[]rune切片解決中文
	arr2 := []rune(str)
	arr2[1] = '我'
	str = string(arr2)
	fmt.Println(str) //H我llo,gogogo

	//練習 斐波那契
	fmt.Println(test(8)) //[1 1 2 3 5 8 13 21]
}

func test(n int) []uint64 {
	var slice []uint64 = make([]uint64, n)
	for i := 0; i < n; i++ {
		if i <= 1 {
			slice[i] = 1
		} else {
			num := slice[i-1] + slice [i-2]
			slice[i] = num
		}
	}
	return slice
}