Go语言入门
学习Go时,发现Go可以将代码写得极其简单,下面是我实现的一个快速排序代码:
// Start from here:
package qsort
func quickSort(values []int, left, right int) {
i, j := left, right
for i != j {
for values[j] >= values[left] && i < j {
j--
}
for values[i] <= values[left] && i < j {
i++
}
if i < j {
values[i], values[j] = values[j], values[i]
}
}
values[left], values[i] = values[i], values[left]
switch {
case i - 1 > left:
quickSort(values, left, i - 1)
case right > i + 1:
quickSort(values, i + 1, right)
}
}
func QuickSort(values []int) {
quickSort(values, 0, len(values) - 1)
}
// End here可以直接调用
# package build …
# package install
然后主程序如下,编译后可以用一个文件来放in and out file
命令行运行:
# sorter -i infile -o outfile -a qsort
就可以了。
package main
import (
"flag"
"fmt"
"io"
"os"
"bufio"
"strconv"
"time"
"algorithm/bubblesort"
"algorithm/qsort"
)
var infile *string = flag.String("i", "infile", "File contains values for sorting")
var outfile *string = flag.String("o", "outfile", "File to receive sorted values")
var algorithm *string = flag.String("a", "qsort", "Sort algorithm")
func readValues(infile string)(values []int, err error) {
file, err := os.Open(infile)
if err != nil {
fmt.Println("Failed to open the input file ", infile)
return
}
defer file.Close()
br := bufio.NewReader(file)
values = make([]int, 0)
for {
line, isPrefix, err1 := br.ReadLine()
if err1 != nil {
if err1 != io.EOF {
err = err1
}
break
}
if isPrefix {
fmt.Println("A too long line, seems unexpected.")
return
}
str := string(line)
value, err1 := strconv.Atoi(str)
if err1 != nil {
err = err1
return
}
values = append(values, value)
}
return
}
func writeValues(values []int, outfile string) error {
file, err :=os.Create(outfile)
if err != nil {
fmt.Println("Failed to create the output file ", outfile)
return err
}
defer file.Close()
for _, value := range values {
str := strconv.Itoa(value)
file.WriteString(str + "\n")
}
return nil
}
func main() {
flag.Parse()
if infile != nil {
fmt.Println("infile =", *infile, "outfile =", *outfile, "algorithm =",
*algorithm)
}
values, err := readValues(*infile)
if err == nil {
t1 := time.Now()
switch *algorithm {
case "qsort":
qsort.QuickSort(values)
case "bubblesort":
bubblesort.BubbleSort(values)
default:
fmt.Println("Sorting algorithm", *algorithm, "is either unknown or unsupported.")
}
t2 := time.Now()
fmt.Println("The sorting process costs", t2.Sub(t1), "to complete.")
writeValues(values, *outfile)
} else {
fmt.Println(err)
}
}