Get possible array combinations

Question

SO,

The problem

From SQL I\'m getting an array with strings (flat array) - let it be

$rgData = [\'foo\', \'bar\', \'baz\', \'bee\         


        

Answer 1

I've just tried to solve this problem with minimum time complexity and without using recursion using go language.

I've seen a few solutions, but with using a recursive function. Avoiding recursion to solve stack size exceeded error.

package main

import "fmt"

func main() {
    // Arguments
    arr := []string{"foo", "bar", "baz", "bee", "feo", "boo", "bak"}
    combinations := make([][]string, 0)
    k := 4
    n := len(arr)

    // Execution starts from here
    if k > n {
        panic("invalid requirement")
    }

    pos := make([]int, k) // this variable is used to plot the unique combination of elements

    // initialize an array with first ever plotting possitions
    i := 0
    c := k
    for c > 0 {
        c--
        pos[i] = c
        i++
    }
    combinations = append(combinations, getCombination(arr, pos, k))

    // Let's begin the work
    x := 0
    ctr := 1 // counter is use to calculate total iterations
    for pos[x] < n-(x+1) {
        ctr++
        pos[x]++

        combinations = append(combinations, getCombination(arr, pos, k))

        if pos[x] == n-(x+1) && x+1 < k {
            x++
            i := x
            s := pos[x] + 1
            for i > 0 {
                i--
                s++
                pos[i] = s
            }

            // continue to next index
            continue
        }

        x = 0

    }

    fmt.Println("total # iterations: --> ", ctr)

    fmt.Println(combinations, "\ntotal # combinations: ", len(combinations))

}

func getCombination(arr []string, pos []int, k int) []string {
    combination := make([]string, k)
    for i, j := k-1, 0; i >= 0; i, j = i-1, j+1 {
        combination[j] = arr[pos[i]]
    }
    return combination
}

The working example is here https://play.golang.org/p/D6I5aq8685-