Print all possible strings in JS

Question

I want to make a functions that prints all the possible combinations from the given string. example: given_string = "ABC" this should print: AAA AAB AAC ABA ABB ABC .. and so on, until it reaches maximum options. CCC

I found some code on the web and modified it for JS

s = ["A", "B", "C"]

function printAllKLength(set, k) {
  n = set.length;
  printAllKLengthRec(set, "", n, k);
}

function printAllKLengthRec(set, prefix, n, k) {
  if (k == 0) {
    console.log(prefix);
    return;
  }
  for (i = 0; i < n; i++) {
    newPrefix = prefix + set[i];
    printAllKLengthRec(set, newPrefix, n, k - 1);
  }
}
printAllKLength(s, 4)

It only changes the last character and I don't understand where is my mistake. original code URL: https://www.geeksforgeeks.org/print-all-combinations-of-given-length/

Talha Akbar · Accepted Answer · 2020-07-12 12:49:20Z

3

While declaring your variables, you have missed out on using the var keyword and especially before declaring i in the for statement. It's important since variables without var keyword are defined in global scope and each recursive call is using the same i variable for the for loop. That's the reason it generates very few possibilities. See the fixed code below:

s = ["A", "B", "C"]

function printAllKLength(set, k) {
  n = set.length;
  printAllKLengthRec(set, "", n, k);
}

function printAllKLengthRec(set, prefix, n, k) {
  if (k == 0) {
    console.log(prefix);
    return;
  }
  for (var i = 0; i < n; i++) {
    // ^^^ Notice var, it scopes the variable to the function otherwise, it will be global 
    newPrefix = prefix + set[i];
    printAllKLengthRec(set, newPrefix, n, k - 1);
  }
}
printAllKLength(s, 4)

answered Jul 12, 2020 at 12:49

Talha Akbar

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Comments

Scott Sauyet · Accepted Answer · 2020-07-13 13:08:06Z

0

Another answer already demonstrated how to fix your code. But I just want to point out a simpler recursion to calculate these values, leaving the printing for a separate step:

const allCombos = (n, xs) =>
  n == 0
    ? ['']
    : allCombos (n - 1, xs) .flatMap (c => xs. map(x => c + x))

console .log (
  allCombos (3, ['A', 'B', 'C']),
)

.as-console-wrapper {min-height: 100% !important; top: 0}

For n-character strings, we simply recur on n - 1 characters, and for each of those, map over the characters, appending each to the string. When n is 0, we simply return an array containing the empty string.

answered Jul 13, 2020 at 13:08

Scott Sauyet

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