Lesson 1 Lab: Prime factors solution

startcode01.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Look for the largest prime number\n",
    "##### The prime factors of 13195 are 5, 7, 13 and 29.\n",
    "##### What is the largest prime factor of the number 600851475143?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[5, 7, 13, 29]\n",
      "29\n",
      "[71, 839, 1471, 6857L]\n",
      "6857\n"
     ]
    }
   ],
   "source": [
    "\"\"\"\n",
    "1.Create a function to get all factors of the number\n",
    "2.In a for-loop of a for-loop in the number, loop in every factor to find their prime factor\n",
    "3.Create a method or find an existing module that can replace the repeating for-loop of each factor -> Generato concept\n",
    "4.Get the max of the results\n",
    "\"\"\"\n",
    "\n",
    "def prime(n):\n",
    "    \"\"\"\n",
    "    To generate all prime factors of the number\n",
    "    \"\"\"\n",
    "    i = 2\n",
    "    while i * i <= n:\n",
    "        while not n % i:\n",
    "            yield i\n",
    "            n /= i\n",
    "        i += 1\n",
    "    if n > 1:\n",
    "        yield n\n",
    "\n",
    "# print prime(13195)\n",
    "# print prime(600851475143)\n",
    "\n",
    "print list(prime(13195))\n",
    "print max(prime(13195))\n",
    "\n",
    "print list(prime(600851475143))\n",
    "print max(prime(600851475143))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Reference:\n",
    "* https://wiki.python.org/moin/Generators\n",
    "* https://www.liaoxuefeng.com/wiki/001374738125095c955c1e6d8bb493182103fac9270762a000/00138681965108490cb4c13182e472f8d87830f13be6e88000\n",
    "* https://stackoverflow.com/questions/19157283/right-algorithm-for-finding-largest-prime-factor\n"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 2",
   "language": "python",
   "name": "python2"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 2
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython2",
   "version": "2.7.11"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}