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")
    }
}

测试结果，每个数字出现在数组各个位置的次数

2 -> 969 1004 999 998 916 1058 983 1028 1042 1003
1 -> 1007 989 1006 991 972 1022 996 1013 995 1009
7 -> 1022 1024 992 1022 1058 956 1028 978 959 961
3 -> 1018 1014 1009 999 1013 945 989 982 1025 1006
4 -> 990 995 1007 1027 981 963 974 993 1003 1067
8 -> 1008 989 1029 963 1037 1036 1036 974 941 987
9 -> 993 1000 979 1018 1040 1021 1020 917 1003 1009
0 -> 1016 993 940 1009 1020 1032 1006 996 988 1000
5 -> 1003 976 1020 977 972 1001 947 1062 1054 988
6 -> 974 1016 1019 996 991 966 1021 1057 990 970