1/22 classroom exercise

scratch.js

// Stock Market Profit
// Source: InterviewCake

// Write an function called getMaxProfit that takes in an array of stock prices and returns the best profit you could have made from 1 purchase and 1 sale. The prices in the array are in the sequence in which they were purchased and can only be sold after it was first purchased.

// Input: getMaxProfit([10, 7, 5, 8, 11, 9])
// Output: 6 ..this is the result of 11 - 5
const getMaxProfit = arr => {
  let max_profit = 0;
  for (let i = 1; i < arr.length; i++) { // buy
    for (let j = i; j < arr.length; j++) { // sell
      if (arr[j] - arr[i] > max_profit) { // buy low, sell high
        max_profit = arr[j] - arr[i];
      }
    }
  }
  
  return max_profit;
}


// DNA Strings
// Source: CodeWars

// In DNA strings, symbols "A" and "T" are complements of each other, as are "C" and "G". 
// Write a function called dnaTransform that takes in a DNA string returns a string that represents it's compliment.
// Input: dnaTransform("ATTGC")
// Output: "TAACG"
const dnaTransform = str => {
  const complement = {
    "A": "T",
    "T": "A",
    "C": "G",
    "G": "C"
  }
  
  return str
    .split('')
    .map(el => {
      if(el in complement) { return complement[el] }  
    })
    .join('');
}


// Randomize An Array
// Source: Fisher-Yates Shuffle
// Write a function called shuffle that given an array, randomizes the position of the elements and returns the new array.
// Input: shuffle(['a','b','c','d'])
// Possible Output: ['b','d','a','c']
const getRandomInt = (min, max) => {
  min = Math.ceil(min);
  max = Math.floor(max);
  
  return Math.floor(Math.random() * (max - min)) + min;
}

const shuffle = array => {
  const upper = array.length;
  let temp, rand;
  for (let lower = 0; lower < upper; lower++) {
    temp = array[lower];
    rand = getRandomInt(lower, length); // generate random index in moving range
    array[lower] = array[rand];
    array[rand] = temp;
  }
  
  return array;
}

// Find The Products
// Source: InterviewCake 
// Write a function called getProducts that takes in an array of n numbers and 
// for each index finds the product of every integer except the integer at that index.
// Input: getProducts([1,2,3,4])
// Output: [ 24, 12, 8, 6 ]
const getProducts = arr => {
  const arr2 = [];
  for (let i = 0; i < arr.length; i++) {
    let temp = arr.slice();
    temp.splice(i,1);
    arr2.push(temp.reduce((curr, acc) => {
      return acc * curr;
    }, 1));
  }
  
  return arr2;
}


// Factorial
// Source: HackerRank
// Given a number, print its factoral.
// Input: 5
// Output: 120 (54321)
const factorial = num => {
  let result = 1;
  for (let i = num; i > 0; i--) {
    result *= i;
  }
  
  return result;
}