go示例1：文件讀寫和排序（快速 冒泡）

package main

import (
	"algorithm/bubblesort"
	"algorithm/qsort"
	"bufio"
	"flag"
	"fmt"
	"io"
	"os"
	"strconv"
	"time"
)

var infile *string = flag.String("i", "unsorted.dat", "File contains values for sorting")
var outfile *string = flag.String("o", "sorted.dat", "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)
		fmt.Print(str, " ")
		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 {
		fmt.Println(err)
	} else {
		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)
	}

}

package bubblesort

func BubbleSort(values []int) {
	for i := 0; i < len(values)-1; i++ {
		for j := 0; j < len(values)-i-1; j++ {
			if values[j] > values[j+1] {
				values[j], values[j+1] = values[j+1], values[j]
			}
		}
	}
}

package qsort

func quickSort(values []int, left, right int) {
	temp := values[left]
	p := left
	i, j := left, right

	for i <= j {
		for j >= p && values[j] >= temp {
			j--
		}
		if j >= p {
			values[p] = values[j]
			p = j
		}
		if values[i] <= temp && i <= p {
			i++
		}

		if i <= p {
			values[p] = values[i]
			p = i
		}
	}

	values[p] = temp  //provKey
	if p-left > 1 {
		quickSort(values, left, p-1)
	}
	if right-p > 1 {
		quickSort(values, p+1, right)
	}
}

func QuickSort(values []int) {
	quickSort(values, 0, len(values)-1)
}