Generate all possible n-character passwords

Question

As part of a learning-Go exercise, I\'m writing a simplistic brute-force password cracker.

To generate all possible 2-character passwords that use the characters A-E in

Answer 1

For example, satisfying your restrictions,

package main

import "fmt"

func nextPassword(n int, c string) func() string {
    r := []rune(c)
    p := make([]rune, n)
    x := make([]int, len(p))
    return func() string {
        p := p[:len(x)]
        for i, xi := range x {
            p[i] = r[xi]
        }
        for i := len(x) - 1; i >= 0; i-- {
            x[i]++
            if x[i] < len(r) {
                break
            }
            x[i] = 0
            if i <= 0 {
                x = x[0:0]
                break
            }
        }
        return string(p)
    }
}

func main() {
    np := nextPassword(2, "ABCDE")
    for {
        pwd := np()
        if len(pwd) == 0 {
            break
        }
        fmt.Println(pwd)
    }
}

Output:

AA
AB
AC
AD
AE
BA
BB
BC
BD
BE
CA
CB
CC
CD
CE
DA
DB
DC
DD
DE
EA
EB
EC
ED
EE