7-26 INTERVIEW Q'S JONATHAN-WILLIAM

1: Numbers less than a given number

Imagine you have an array of numbers. Write an algorithm to remove all numbers less than five from the array. You shouldn't use the .filter method here; try to write the algorithm from scratch.

const arr = [1,2,3,4,5,6,7,8,9,10];

const remLessThan = (arr, value) => {
  const newArr = [];
  arr.forEach(item => {
    if(item >= value) {
      newArr.push(item);
    }
  });
  return newArr;
}

console.log(remLessThan(arr, 5));

Runtime: Linear // O(n) - We don't think this needs to be optimized further.




2: Merge Arrays

Imagine you have two arrays which have already been sorted. Write an algorithm to merge the two arrays into a single array, which should also be sorted. For example, if your input arrays were [1, 3, 6, 8, 11] and [2, 3, 5, 8, 9, 10], your output array should be [1, 2, 3, 3, 5, 6, 8, 8, 9, 10, 11].

const arr1= [1, 3, 6, 8, 11];
const arr2= [2, 3, 5, 8, 9, 10];

function merge(arr1, arr2){
  let d1 = 0;
  let d2 = 0;
  const returnArr = [];
  
  while(d1 < arr1.length && d2 < arr2.length){
    if(arr1[d1] > arr2[d2]){
      returnArr.push(arr2[d2++]);
    }
    else{
      returnArr.push(arr1[d1++]);
    }
  }
  
  while(d1 < arr1.length) {
    returnArr.push(arr1[d1++]);
  }
  
  while(d2 < arr2.length) {
    returnArr.push(arr2[d2++]);
  }
  console.log(returnArr);
}

merge(arr1,arr2);

Runtime: Linear // O(n) - We don't think this could be optimized further



3: Remove Characters

Write an algorithm that deletes given characters from a string. For example, given a string of "Battle of the Vowels: Hawaii vs. Grozny" and characters to be removed are "aeiou", the algorithm should transform the original string to "Bttl f th Vwls: Hw vs. Grzny".

const str = "Battle of the Vowels: Hawaii vs. Grozny"
// const rem = /[aeiou]/;
const rem = "aeiou";
let tick = 0;
function remover(str,rem){
  let returnString = '';
  let d1 = 0;
  let d2 = 0;
  while(d1 < str.length) {
    tick++
    if(str[d1] !== rem[d2] && d2 === rem.length) {
      returnString += str[d1++];
      d2 = 0;
    }
    else if(str[d1] === rem[d2]){
      d1++;
      d2 =0;
    }
    else {
      d2++;
    }
  }
  
  console.log(returnString);
}

remover(str,rem);

Runtime: quadratic O(n^2) - Yikes.




4: Products

Given an array of numbers, write an algorithm to find out the products of every number, except the one at that index. For example, if the input was [1, 3, 9, 4], the output should be [108, 36, 12, 27] (i.e. [394, 194, 134, 139]).

const arr = [1, 3, 9, 4, 5, 8];

function products(arr){
  let product = 1;
  let result = [];
  let ticks = 0;
  arr.forEach(number => {
    ticks++;
    product *= number;
  });
  
  arr.forEach(number => {
    ticks++;
    let devided = product/number;
    result.push(devided);
  });
  console.log(result, ticks);
}

products(arr);

Runtime: Linear // O(n) - Even though it loops TWICE over the same array, adding a new item to the array will only increase the number of iterations by 2 - so in direct proportion. Thus, linear.




5: Appointment Book

Write a program that keeps track of your appointment for the day from 8 am - 7 pm for up to 5 days.Your program will allow users to choose a day between Mon-Fri and an hour between 8 am - 7 pm to add the appointment in the appointment book. Use a multi dimentional array to solve this problem. You don't have to have a fancy UI for this, although you are welcome to use React to create a nice GUI and user input and result. Otherwise simple JS with some input boxes and/or checkboxes will do. A very simple example of your output can look like this

const schedule = [[[],[],[],[],[],[],[],[],[],[],[],[]],[[],[],[],[],[],[],[],[],[],[],[],[]],[[],[],[],[],[],[],[],[],[],[],[],[]],[[],[],[],[],[],[],[],[],[],[],[],[]],[[],[],[],[],[],[],[],[],[],[],[],[]],[[],[],[],[],[],[],[],[],[],[],[],[]],[[],[],[],[],[],[],[],[],[],[],[],[]]]

function input(day,time,input){
  schedule[day][time] = input;
}

function output(day){
  let time = 8
  for(let i=0; i < schedule[day].length; i++){
    console.log(`${time}:00 >>>`,schedule[day][i])
    time++
  }
}

input(0,3,'lol');
output(0);

Runtime: Uhhhh... the first one is O(1), the second is O(n)... can't get much better than that.