go runtime中的洗牌算法测试

## go_shuffle.go
package main

import (
    "math/rand"
    "time"
    "fmt"
)

var report map[int][]int

func shuffle(r *rand.Rand) {
    var data [10]int

    for i := 0; i < 10; i++ {
        data[i] = i
    }
    for i := 0; i < 10; i++ {
        o := data[i]
        j := r.Int() % (i + 1)
        data[i] = data[j]
        data[j] = o
    }

    for i := 0; i < 10; i++ {
        pos_list := report[data[i]]
        pos_list[i]++
    }
}

func main() {
    // init
    report = make(map[int][]int, 10)
    for i := 0; i < 10; i++ {
        report[i] = make([]int, 10)
    }

    // shuffling
    src := rand.NewSource(time.Now().UnixNano())
    r := rand.New(src)
    for n := 0; n < 10000; n++ {
        shuffle(r)
    }

    // report result
    for k, v := range report {
        fmt.Printf("%d -> ", k)
        for _, p := range v {
            fmt.Printf("%5d ", p)
        }
        fmt.Printf("\n")
    }
}