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// run
// Copyright 2024 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
func main() {
err := run()
if err != nil {
panic(err)
}
}
func run() error {
methods := "AB"
type node struct {
tag string
choices []string
}
all := []node{
{"000", permutations(methods)},
}
next := 1
for len(all) > 0 {
cur := all[0]
k := copy(all, all[1:])
all = all[:k]
if len(cur.choices) == 1 {
continue
}
var bestM map[byte][]string
bMax := len(cur.choices) + 1
bMin := -1
for sel := range selections(methods) {
m := make(map[byte][]string)
for _, order := range cur.choices {
x := findFirstMatch(order, sel)
m[x] = append(m[x], order)
}
min := len(cur.choices) + 1
max := -1
for _, v := range m {
if len(v) < min {
min = len(v)
}
if len(v) > max {
max = len(v)
}
}
if max < bMax || (max == bMax && min > bMin) {
bestM = m
bMin = min
bMax = max
}
}
if bMax == len(cur.choices) {
continue
}
cc := Keys(bestM)
for c := range cc {
choices := bestM[c]
next++
switch c {
case 'A':
case 'B':
default:
panic("unexpected selector type " + string(c))
}
all = append(all, node{"", choices})
}
}
return nil
}
func permutations(s string) []string {
if len(s) <= 1 {
return []string{s}
}
var result []string
for i, char := range s {
rest := s[:i] + s[i+1:]
for _, perm := range permutations(rest) {
result = append(result, string(char)+perm)
}
}
return result
}
type Seq[V any] func(yield func(V) bool)
func selections(s string) Seq[string] {
return func(yield func(string) bool) {
for bits := 1; bits < 1<<len(s); bits++ {
var choice string
for j, char := range s {
if bits&(1<<j) != 0 {
choice += string(char)
}
}
if !yield(choice) {
break
}
}
}
}
func findFirstMatch(order, sel string) byte {
for _, c := range order {
return byte(c)
}
return 0
}
func Keys[Map ~map[K]V, K comparable, V any](m Map) Seq[K] {
return func(yield func(K) bool) {
for k := range m {
if !yield(k) {
return
}
}
}
}
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