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combineWithRepetitions.js
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combineWithRepetitions.js
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/**
* @param {*[]} comboOptions
* @param {number} comboLength
* @return {*[]}
*/
export default function combineWithRepetitions(comboOptions, comboLength) {
// If the length of the combination is 1 then each element of the original array
// is a combination itself.
if (comboLength === 1) {
return comboOptions.map(comboOption => [comboOption]);
}
// Init combinations array.
const combos = [];
// Remember characters one by one and concatenate them to combinations of smaller lengths.
// We don't extract elements here because the repetitions are allowed.
comboOptions.forEach((currentOption, optionIndex) => {
// Generate combinations of smaller size.
const smallerCombos = combineWithRepetitions(
comboOptions.slice(optionIndex),
comboLength - 1,
);
// Concatenate currentOption with all combinations of smaller size.
smallerCombos.forEach((smallerCombo) => {
combos.push([currentOption].concat(smallerCombo));
});
});
return combos;
}