const uniqueWithSum = arr =>
arr.reduce((acc, n) => {
const keys = n.slice(0, -1);
const item = acc.find(m => m.length === n.length && keys.every((k, i) => k === m[i]));
(item ?? (acc[acc.length] = [ ...keys, 0 ]))[keys.length] += n[keys.length];
return acc;
}, []);
или
const uniqueWithSum = (function(arr) {
const indexTree = new Map;
return arr.reduce((acc, [...keys]) => {
const val = keys.pop();
const indexes = keys.reduce((p, c) => p.set(c, p.get(c) ?? new Map).get(c), indexTree);
const index = indexes.set(this, indexes.get(this) ?? ~-acc.push([ ...keys, 0 ])).get(this);
acc[index][keys.length] += val;
return acc;
}, []);
}).bind(Symbol());
или
const uniqueWithSum = arr =>
[...arr.reduce((acc, n) => {
const end = n.length - 1;
const key = n.reduce((p, c, i) => i === end ? p : p.set(c, p.get(c) ?? new Map).get(c), acc[0]);
acc[1].set(key, acc[1].get(key) ?? n.map((m, i) => i !== end && m)).get(key)[end] += n[end];
return acc;
}, [ new Map, new Map ])[1].values()];
