python教程分享Go语言切片常考的面试真题解析

目录

• 前言
• 01. 数组和切片有什么区别?
• 02. 拷贝大切片一定比拷贝小切片代价大吗?
• 03. 切片的深浅拷贝
• 04. 零切片、空切片、nil切片是什么
• 05. 切片的扩容策略
• 07. 参数传递切片和切片指针有什么区别?
• 08. range遍历切片有什么要注意的?
• 总结

var buffer [255]int  buffer := [255]int{0}  

var slice []int // 直接声明  slice := []int{1,2,3,4,5} // 字面量方式  slice := make([]int, 5, 10) // make创建  slice := array[1:5] // 截取下标的方式  slice := *new([]int) // new一个  

func main()  {   param1 := make([]int, 100)   param2 := make([]int, 100000000)   smallslice(param1)   largeslice(param2)  }    func smallslice(params []int)  {   // ....  }    func largeslice(params []int)  {   // ....  }

type sliceheader struct {   data uintptr   len  int   cap  int  }

slice := make([]int,5) // 0 0 0 0 0  slice := make([]*int,5) // nil nil nil nil nil  

var slice []int  var slice = *new([]int)  

var slice = []int{}  var slice = make([]int, 0)  

// base address for all 0-byte allocations  var zerobase uintptr    // 分配对象内存  func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.pointer {   ...   if size == 0 {    return unsafe.pointer(&zerobase)   }    ...  }

// runtime/slice.go  // et：表示slice的一个元素；old：表示旧的slice；cap：表示新切片需要的容量；  func growslice(et *_type, old slice, cap int) slice {   if cap  doublecap {    newcap = cap   } else {      // 原 slice 容量小于 1024 的时候，新 slice 容量按2倍扩容    if old.cap <1024 {     newcap = doublecap    } else { // 原 slice 容量超过 1024，新 slice 容量变成原来的1.25倍。     // check 0  maxalloc    newcap = int(capmem)   case et.size == sys.ptrsize:    lenmem = uintptr(old.len) * sys.ptrsize    newlenmem = uintptr(cap) * sys.ptrsize    capmem = roundupsize(uintptr(newcap) * sys.ptrsize)    overflow = uintptr(newcap) > maxalloc/sys.ptrsize    newcap = int(capmem / sys.ptrsize)   case ispoweroftwo(et.size):    var shift uintptr    if sys.ptrsize == 8 {     // mask shift for better code generation.     shift = uintptr(sys.ctz64(uint64(et.size))) & 63    } else {     shift = uintptr(sys.ctz32(uint32(et.size))) & 31    }    lenmem = uintptr(old.len) < (maxalloc >> shift)    newcap = int(capmem >> shift)   default:    lenmem = uintptr(old.len) * et.size    newlenmem = uintptr(cap) * et.size    capmem, overflow = math.muluintptr(et.size, uintptr(newcap))    capmem = roundupsize(capmem)    newcap = int(capmem / et.size)   }  }

type sliceheader struct {   data uintptr   len  int   cap  int  }  

func modifyslice(s []string)  {   s[0] = "song"   s[1] = "golang"   fmt.println("out slice: ", s)  }    func main()  {   s := []string{"asong", "golang梦工厂"}   modifyslice(s)   fmt.println("inner slice: ", s)  }  // 运行结果  out slice:  [song golang]  inner slice:  [song golang]

func appendslice(s []string)  {   s = append(s, "快关注！！")   fmt.println("out slice: ", s)  }    func main()  {   s := []string{"asong", "golang梦工厂"}   appendslice(s)   fmt.println("inner slice: ", s)  }  // 运行结果  out slice:  [asong golang梦工厂 快关注！！]  inner slice:  [asong golang梦工厂]

for k,v := range _ { }  for k := range _ { }  

s := []int{1, 2}  for k, v := range s {      }  会被编译器认为是  for_temp := s  len_temp := len(for_temp)  for index_temp := 0; index_temp 

package main    import (   "fmt"  )    type user struct {   name string   age uint64  }    func main()  {   u := []user{    {"asong",23},    {"song",19},    {"asong2020",18},   }   for _,v := range u{    if v.age != 18{     v.age = 20    }   }   fmt.println(u)  }  // 运行结果  [{asong 23} {song 19} {asong2020 18}]