let set = [1, 2, 3, 4];
let partialCombination = [];
function findCombinations(set, partialCombination) {
for (let i = 0; i < set.length; i++) {
const newPartialCombination = partialCombination.concat(set[i]);
findCombinations(set.slice(i + 1), newPartialCombination);
console.log(newPartialCombination);
}
}
findCombinations(set, partialCombination);After some thinking, I finally mentally understand this algorithm. Iterating all items of the set and in each iteration find all possible combinations of the current item by recursion; recursion process the same problem but with a samller set that excludes all items before the current item, until the set is empty it unwinds. But I can’t desribe it simultaneously understandable and precisely respect to its logic. Please help, if you can state it in understanble English, but also exactly according to its logic. Please don’t give sequence execution explanations, I need conceptual descriptions.
// 1. To find all combinations of the set is equal to
// find all combinations include each item of the set;
// For example set = [a, b, c], then all combinations include a,
// all combinations include b, and all combinations inlcude c together
// are all combinations of the set;
// 2. To find all combinations inlcude the current item is equal to
// find all the combinations of a new set that excludes the current item
// then concatenating them with the current item, and adding the current item itself;
// For example set = [a, b, c], then all combinations include a is
// [a] concatenating with all combinations ([b, c], [b], [c]) of set [b ,c]:
// [a, b, c], [a, b], [a, c] + [a].
// 3. Then to find all combinations of a set, iterating all items of the set,
// finding all combinations of the current item, converting the problem to find all
// combinations of a smaller set which excludes the current item;
// continuing until the set is empty it indicates all combinations for the current item have found,
// the next item can be processed.