PermuteStrings() - fn to generate a string array of all combinations of input string slices, maintaining order

permute_strings.go

// -----------------------------------------------------------------------------
// (c) balarabe@protonmail.com                                      License: MIT
// :v: 2018-03-18 23:55:24                                  [permute_strings.go]
// -----------------------------------------------------------------------------

package main

import "bytes"   // standard
import "fmt"     // standard
import "testing" // standard

func PermuteStrings(parts ...[]string) (ret []string) {
    {
        var n = 1
        for _, ar := range parts {
            n *= len(ar)
        }
        ret = make([]string, 0, n)
    }
    var at = make([]int, len(parts))
    var buf bytes.Buffer
loop:
    for {
        // increment position counters
        for i := len(parts) - 1; i >= 0; i-- {
            if at[i] > 0 && at[i] >= len(parts[i]) {
                if i == 0 || (i == 1 && at[i-1] == len(parts[0])-1) {
                    break loop
                }
                at[i] = 0
                at[i-1]++
            }
        }
        // construct permutated string
        buf.Reset()
        for i, ar := range parts {
            var p = at[i]
            if p >= 0 && p < len(ar) {
                buf.WriteString(ar[p])
            }
        }
        ret = append(ret, buf.String())
        at[len(parts)-1]++
    }
    return ret
}

// go test --run Test_PermuteStrings_
func Test_PermuteStrings_(t *testing.T) {
    var ar = PermuteStrings(
        []string{"11", "22", "33"},
        []string{},
        []string{"AA", "BB", "CC"},
        []string{"XX", "YY"},
    )
    fmt.Println("RESULT:")
    for _, s := range ar {
        fmt.Println("-->", s)
    }
}

/*
RESULT:
--> 11AAXX
--> 11AAYY
--> 11BBXX
--> 11BBYY
--> 11CCXX
--> 11CCYY
--> 22AAXX
--> 22AAYY
--> 22BBXX
--> 22BBYY
--> 22CCXX
--> 22CCYY
--> 33AAXX
--> 33AAYY
--> 33BBXX
--> 33BBYY
--> 33CCXX
--> 33CCYY
*/

//end