日能研の問題をGo言語で力づくで解いてみた(2018/11) ref: https://qiita.com/spiegel-im-spiegel/items/90332789f8a6f98c670d

file0.go

package main

import "fmt"

func Permutations(cards []int) <-chan []int {
    ch := make(chan []int)
    go func() {
        defer close(ch)
        perm(ch, make([]int, 0, len(cards)), cards)
    }()
    return ch
}
func dup(list []int) []int {
    l := make([]int, len(list), cap(list))
    copy(l, list)
    return l
}
func perm(ch chan<- []int, list []int, rest []int) {
    if len(rest) == 0 {
        ch <- dup(list)
        return
    }
    for i, v := range rest {
        restx := dup(rest)
        restx = append(restx[:i], restx[i+1:]...)
        listx := append(list, v)
        perm(ch, listx, restx)
    }

}

func list2num(list []int) int {
    v := 0
    for i, t := len(list)-1, 1; i >= 0; i, t = i-1, t*10 {
        v += list[i] * t
    }
    return v
}
func main() {
    for p := range Permutations([]int{1, 2, 3, 4, 5, 6}) {
        res := true
        for i := 2; i <= 6; i++ {
            if list2num(p[:i])%i != 0 {
                res = false
                break
            }
        }
        if res {
            fmt.Println(list2num(p))
        }
    }
}