Use min-heap to find lowest range spanning four lists - Javascript

min-heap-range-four-lists.js

"use strict";

const Heap = require("heap")

const input = [
  [3, 6, 8, 10 , 15],
  [1, 5, 12],
  [4, 8, 15, 16],
  [2, 6]  
]

const h = new Heap((a, b) => a.v - b.v);
input.forEach((list, idx) => h.push({v: list.shift(), idx}));

let current;
let ranges = [];
let exhausted = false;

let highest = Math.max(...h.toArray().map(_ => _.v));

while (!exhausted) {
  current = h.pop();
  ranges.push([current.v, highest]);
  
  const v = input[current.idx].shift();  
  if (v) {
    highest = Math.max(highest, v);
    h.push({v, idx: current.idx});
    continue;
  }
  
  exhausted = true;
}

console.log(ranges)