examples/project-euler.html at master · chinhdo/examples · GitHub

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<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="utf-8" />

  <title>Project Euler Solutions</title>
  <meta name="description" content="TODO" />
  <meta name="author" content="Chinh Do" />
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    rel="stylesheet" />
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  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
  <style>
    /* RESET */
    /* Box sizing rules */
    *,
    *::before,
    *::after {
      box-sizing: border-box;
    }

    html,
    body {
      font-family: "Roboto", sans-serif;
      margin: 0;
      background-color: #222222;
      color: white;
    }

    a {
      color: white;
      text-decoration: none;
    }

    li {
      padding: 2px;
    }

    h1 {
      font-size: 1.5rem;
    }

    .container {
      padding: 20px;
    }

    .answer {
      color: green
    }
  </style>
</head>

<body>
  <div class="container">
    <h1>Project Euler Problems & Chinh's Solutions</h1>
    <h2><a href="https://projecteuler.net/problem=1">Multiples of 3 and 5</a></h2>
    <p>If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these
      multiples is 23.</p>
    <p>Find the sum of all the multiples of 3 or 5 below 1000.</p>
    <p>Answer: <span class="answer" id="p1"></span></p>

    <h2><a href="https://projecteuler.net/problem=2">Even Fibonacci numbers</a></h2>
    <p>Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2,
      the first 10 terms will be: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...</p>
    <p>By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the
      even-valued terms.</p>
    <p>Answer: <span class="answer" id="p2"></span></p>

    <h2><a href="https://projecteuler.net/problem=3">Largest prime factor</a></h2>
    <p>The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ?</p>
    <p>Answer: <span class="answer" id="p3"></span></p>

    <h2><a href="https://projecteuler.net/problem=4">Largest palindrome product</a></h2>
    <p>A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit
      numbers is 9009 = 91 × 99.

      Find the largest palindrome made from the product of two 3-digit numbers.</p>
    <p>Answer: <span class="answer" id="p4"></span></p>

    <p><a href="https://github.com/chinhdo/examples/blob/master/project-euler.html">GitHub</a></p>
  </div>
  <script>
    $(function () {
      p1();
      p2();
      p3LargestPrimeFactor();
      p4LargestPalindrome();
    });

    function p4LargestPalindrome() {
      let max = 0;
      for (let i = 999; i >= 100; i--) {
        for (let j = 999; j >= 100; j--) {
          const p = i * j;
          const str = p.toString();
          const reversed = str.split('').reverse().join('');

          if (str === reversed) {
            if (p > max) {
              max = p;
            }
          }
        }
      }

      $("#p4").text(max);
    }

    // The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ?
    function p3LargestPrimeFactor() {
      let x = 600851475143;
      let y = 2;
      let factor = 0;

      while (true) {
        if (x % y === 0 && isPrime(y)) {
          factor = y;
        }

        y++;

        if (y > Math.sqrt(x)) break;
      }

      $("#p3").text(factor);
    }

    function p1() {
      let sum = 0;
      for (let i = 0; i < 1000; i++) {
        if (i % 3 === 0 || i % 5 === 0) {
          sum += i;
        }
      }

      $("#p1").text(sum);
    }

    function p2() {
      let sum = 2;
      let n1 = 1;
      let n2 = 2;
      let i = 0;
      while (true) {
        const n3 = n1 + n2;
        if (n3 % 2 === 0) {
          sum += n3;
        }

        n1 = n2;
        n2 = n3;

        if (n3 > 4000000) {
          break;
        }
      }

      $("#p2").text(sum);
    }

    const isPrime = num => {
      for (let i = 2; i < num; i++)
        if (num % i === 0) return false;
      return num > 1;
    }
  </script>
</body>

</html>