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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})
}
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