Generate all string of given length, from given characters

Question

I want to generate string of given length, from given characters. The order of the characters matters, also I want to use multiple threads to generate it. Here are a few examples:

chars: a,b,c,d
length: 1
output: 
a
b
c
d
chars: a,b,c,d
length: 2
output:
aa
ab
ac
ad
bb
ba
bc
bd
cc
ca
cb
cd
dd
da
db
dc

I've tried this algorithm: Note: it's pseudo-code

func generate(set, str, k){
    if (k == 0){
        print str;
        return;
    }
    for (c in set) {
        newString = str + c;
        generate(set, newString, k-1);
    }
}

However I don't see how to use multiple threads. All other algorithms I've read about don't suite my needs.

tag your question properly and show what you've researched and tried — dbmitch, Jul 06 '16 at 17:24
I don't care about the programming language as long as it isn't something like brainfuck. — Deyan Georgiev, Jul 06 '16 at 17:28
Python has [`itertools.product`](https://docs.python.org/3/library/itertools.html#itertools.product), you can iterate over `itertools.product('abcd', repeat=2)` to get your second desired output. — Antti Haapala -- Слава Україні, Jul 06 '16 at 17:41
Mind explaining further, If i can understand correctly, with itertools.product('abcd', repeat=2) I get 'ab'? — Deyan Georgiev, Jul 06 '16 at 17:45
In case anybody came here with the search engine. Here is how to make the product multithreaded http://stackoverflow.com/questions/10262138/how-do-i-multi-process-the-itertools-product-module — Deyan Georgiev, Jul 06 '16 at 18:00

score 0 · Answer 1 · answered Jul 06 '16 at 18:04

0

No need of use multithreading for this algorithm. The for loop is only for generating string for required length. In java the code is like this.

import java.util.Random;

public class RandomString2 {

static String[] option = {"a","b","v","k"}; 

static String getRandomElement()
{
    int idx = new Random().nextInt(option.length);
    return option[idx];
}

static String getRandomString(int length)
{
    String result="";
    for(int i = 1; i<=length ; i++)
    {
        result += getRandomElement();
    }
    return result;
}

public static void main(String[] args) {
    // TODO Auto-generated method stub

    System.out.println(getRandomString(5));  // pass string length as parameter

}

}

answered Jul 06 '16 at 18:04

Shahbaz Hashmi

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I want to make the algorithm multi threaded, since I'm planning to use it for a lot of combinations. – Deyan Georgiev Jul 06 '16 at 18:11
I dont know what are you planning to execute. But multithreading is used for separate path of execution. I had answered to your particular question. It will be better that u post some code. – Shahbaz Hashmi Jul 06 '16 at 18:19
Well it's possible that I have so misunderstaning of what multithreading is. However what I want is to split the computation between multiple threads/processors, so that I can compute the result faster. – Deyan Georgiev Jul 06 '16 at 18:50

Generate all string of given length, from given characters

1 Answers1