几种比较好的 goLang 排列组合方法推荐
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// Port of some Python's itertools
// ================================
// A.K.A. my first piece of Go code
//
// Written by Nuno Antunes, 2012-08-08
// GitHub: https://github.com/ntns
//
// Python docs: http://docs.python.org/library/itertools.html
// Python source: http://svn.python.org/view/python/tags/r271/Modules/itertoolsmodule.c?view=markup
package main
import "fmt"
func combinations(iterable []int, r int) {
pool := iterable
n := len(pool)
if r > n {
return
}
indices := make([]int, r)
for i := range indices {
indices[i] = i
}
result := make([]int, r)
for i, el := range indices {
result[i] = pool[el]
}
fmt.Println(result)
for {
i := r - 1
for ; i >= 0 && indices[i] == i+n-r; i -= 1 {
}
if i < 0 {
return
}
indices[i] += 1
for j := i + 1; j < r; j += 1 {
indices[j] = indices[j-1] + 1
}
for ; i < len(indices); i += 1 {
result[i] = pool[indices[i]]
}
fmt.Println(result)
}
}
func permutations(iterable []int, r int) {
pool := iterable
n := len(pool)
if r > n {
return
}
indices := make([]int, n)
for i := range indices {
indices[i] = i
}
cycles := make([]int, r)
for i := range cycles {
cycles[i] = n - i
}
result := make([]int, r)
for i, el := range indices[:r] {
result[i] = pool[el]
}
fmt.Println(result)
for n > 0 {
i := r - 1
for ; i >= 0; i -= 1 {
cycles[i] -= 1
if cycles[i] == 0 {
index := indices[i]
for j := i; j < n-1; j += 1 {
indices[j] = indices[j+1]
}
indices[n-1] = index
cycles[i] = n - i
} else {
j := cycles[i]
indices[i], indices[n-j] = indices[n-j], indices[i]
for k := i; k < r; k += 1 {
result[k] = pool[indices[k]]
}
fmt.Println(result)
break
}
}
if i < 0 {
return
}
}
}
func product(argsA, argsB []int) {
pools := [][]int{argsA, argsB}
npools := len(pools)
indices := make([]int, npools)
result := make([]int, npools)
for i := range result {
result[i] = pools[i][0]
}
fmt.Println(result)
for {
i := npools - 1
for ; i >= 0; i -= 1 {
pool := pools[i]
indices[i] += 1
if indices[i] == len(pool) {
indices[i] = 0
result[i] = pool[0]
} else {
result[i] = pool[indices[i]]
break
}
}
if i < 0 {
return
}
fmt.Println(result)
}
}
func main() {
fmt.Println("Itertools combinations in Go:")
// combinations('ABCD', 2) --> AB AC AD BC BD CD
// combinations(range(4), 3) --> 012 013 023 123
fmt.Printf("iterable = %s, r = %d", "[]int{1, 2, 3, 4, 5, 6}", 3)
fmt.Println()
combinations([]int{1, 2, 3, 4, 5, 6}, 3)
fmt.Println("Itertools permutations in Go:")
// permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC
// permutations(range(3)) --> 012 021 102 120 201 210
fmt.Printf("iterable = %s, r = %d", "[]int{1, 2, 3, 4}", 3)
fmt.Println()
permutations([]int{1, 2, 3, 4}, 3)
fmt.Println("Itertools product in Go:")
// product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy
// product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111
fmt.Printf("iterables = %s, %s", "[]int{1, 2, 3}", "[]int{10, 20, 30}")
fmt.Println()
product([]int{1, 2, 3}, []int{10, 20, 30})
}
运行输出：
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Itertools combinations in Go:
iterable = []int{1, 2, 3, 4, 5, 6}, r = 3
[1 2 3]
[1 2 4]
[1 2 5]
[1 2 6]
[1 3 4]
[1 3 5]
[1 3 6]
[1 4 5]
[1 4 6]
[1 5 6]
[2 3 4]
[2 3 5]
[2 3 6]
[2 4 5]
[2 4 6]
[2 5 6]
[3 4 5]
[3 4 6]
[3 5 6]
[4 5 6]
Itertools permutations in Go:
iterable = []int{1, 2, 3, 4}, r = 3
[1 2 3]
[1 2 4]
[1 3 2]
[1 3 4]
[1 4 2]
[1 4 3]
[2 1 3]
[2 1 4]
[2 3 1]
[2 3 4]
[2 4 1]
[2 4 3]
[3 1 2]
[3 1 4]
[3 2 1]
[3 2 4]
[3 4 1]
[3 4 2]
[4 1 2]
[4 1 3]
[4 2 1]
[4 2 3]
[4 3 1]
[4 3 2]
Itertools product in Go:
iterables = []int{1, 2, 3}, []int{10, 20, 30}
[1 10]
[1 20]
[1 30]
[2 10]
[2 20]
[2 30]
[3 10]
[3 20]
[3 30]
这里有另外一个实现： https://github.com/kokardy/listing
使用方法：
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package main
import (
"fmt"
"github.com/kokardy/listing"
)
func main() {
ss := listing.StringReplacer([]string{
"A", "B", "C", "D",
})
//You can use any types that implement listing.Replacer interface (Len(), Replace([]int))
select_num := 3
repeatable := false
buf := 5
fmt.Println("Permutations")
for perm := range listing.Permutations(ss, select_num, repeatable, buf) {
fmt.Println(perm)
}
fmt.Println("Combinations")
for comb := range listing.Combinations(ss, select_num, repeatable, buf) {
fmt.Println(comb)
}
}
输出：
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Permutations
[A B C]
[A C B]
[B A C]
[B C A]
[C A B]
[C B A]
[A B D]
[A D B]
[B A D]
[B D A]
[D A B]
[D B A]
[A C D]
[A D C]
[C A D]
[C D A]
[D A C]
[D C A]
[B C D]
[B D C]
[C B D]
[C D B]
[D B C]
[D C B]
Combinations
[A B C]
[A B D]
[A C D]
[B C D]
更简单的实现：
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package main
import (
"fmt"
)
func main() {
comb(5, 3, func(c []int) {
fmt.Println(c)
})
}
func comb(n, m int, emit func([]int)) {
s := make([]int, m)
last := m - 1
var rc func(int, int)
rc = func(i, next int) {
for j := next; j < n; j++ {
s[i] = j
if i == last {
emit(s)
} else {
rc(i+1, j+1)
}
}
return
}
rc(0, 0)
}
输出：
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[0 1 2]
[0 1 3]
[0 1 4]
[0 2 3]
[0 2 4]
[0 3 4]
[1 2 3]
[1 2 4]
[1 3 4]
[2 3 4]