AlgoExpert Largest Range - https://www.algoexpert.io/questions/Largest%20Range

algoexpert-largest-range.js

function largestRange(array) {
  if (array.length === 1) {
    return [array[0], array[0]];
  }

  var hash = {};
  hash[array[0]] = [];
  var current = array[0];
  for (var i = 1; i < array.length; i++) {
    var temp = array[i];
    if (!hash[temp]) {
      hash[temp] = [];
    }

    if (hash[temp - 1]) {
      hash[temp].push(temp - 1);
    }

    if (hash[temp + 1]) {
      hash[temp].push(temp + 1);
    }

    if (hash[temp - 1]) {
      hash[temp - 1].push(temp);
    }

    if (hash[temp + 1]) {
      hash[temp + 1].unshift(temp);
    }
  }

  var keys = Object.keys(hash), max = [];
  for (var i = 0; i < keys.length; i++) {
    var key = keys[i];
    var arr = hash[key];
    if (arr.length === 1 && arr[0] > key) {
      var a = hash[arr[0]], temp = [parseInt(key), arr[0]];
      for (var j = 1; j < keys.length; j++) {
        if (!a || !a.length || a.length === 1) {
          break;
        }
        if (a[a.length - 1]) {
          temp.push(a[a.length - 1]);
        }
        a = hash[a[a.length - 1]];
      }
      if (temp.length > max.length) {
        max = temp;
      }
    }
  }

  return [max[0], max[max.length - 1]];
}