Thanks Ian,
You are correct (although the post I submitted yesterday had the clobbering
lines incorrect - that was one of my experiments to see if rebuilding the
3D slice differently would overcome the problem). The code below is my
original.
Yes, the function works by building fresh versions of out at each later and
then reconstructing each set from the returned outs.
I am currently assuming that because it works for 2, 3, and 4 then somehow
I'm doing something that causes my Go runtime (latest version running on
Linux Mint 18 on an Intel i5) to return an answer before it has finished
producing sets.
My next experiments will be to try to use the Gogland debug to establish
why it stops.
package main
import (
"fmt"
"time")
func get_partitions(set []string, out [][][]string) [][][]string {
out = make([][][]string, 1)
out[0] = make([][]string, 1)
out[0][0] = make([]string, 0)
if len(set) <= 1 {
out[0][0] = set
return out
}
for j := 0; j < len(set)*len(set)/2; j++ {
i := j
parts := make([][]string, 2)
for _, item := range set {
parts[i&1] = append(parts[i&1], item)
i >>= 1
}
pts := get_partitions(parts[1], out)
for _, pt := range pts {
i3 := len(out) - 1
if len(out[i3][len(out[i3])-1]) == 0 {
out[i3][len(out[i3])-1] = parts[0]
} else {
out = append(out, [][]string{})
i3 += 1
out[i3] = append(out[i3], parts[0])
}
if len(pt[0]) > 0 {
for ptidx, _ := range pt {
out[i3] = append(out[i3], pt[ptidx])
}
}
}
}
return out}
func main() {
set := []string{"1", "2", "3", "4", "5"}
var out, ppp [][][]string
out = make([][][]string, 1) // create & initialize 3D slice
out[0] = make([][]string, 1)
out[0][0] = make([]string, 1)
t0 := time.Now()
ppp = get_partitions(set, out)
elapsed := time.Since(t0)
fmt.Printf("Took %s\n", elapsed)
fmt.Printf("\nGot the partition: %v\n", ppp)
fmt.Println(len(ppp))}
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