{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# Word chains\n", "\n", "\"Word chain\" puzzles are where you transform one word into another, by changing one letter at a time, with all the intermediate steps being valid words. \n", "\n", "For instance, you can transform 'rash' to 'jags' like this:\n", "\n", "```\n", "rash\n", "Bash\n", "basS\n", "baGs\n", "Jags\n", "```\n", "\n", "(the capital letter is the one changed in each step).\n", "\n", "## Part 1\n", "\n", "Given this [list of words](words4.txt), what is the minimum number of steps to go from `vice` to `wars`?" ] }, { "cell_type": "code", "execution_count": 1, "metadata": { "collapsed": true }, "outputs": [], "source": [ "import string\n", "import heapq" ] }, { "cell_type": "code", "execution_count": 2, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "2336" ] }, "execution_count": 2, "metadata": {}, "output_type": "execute_result" } ], "source": [ "words = [w.strip() for w in open('08-rooms.txt').readlines()]\n", "len(words)" ] }, { "cell_type": "code", "execution_count": 3, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def adjacents(word):\n", " return [word[0:i] + l + word[i+1:]\n", " for i in range(len(word))\n", " for l in string.ascii_lowercase\n", " if l != word[i]]" ] }, { "cell_type": "code", "execution_count": 4, "metadata": { "collapsed": true }, "outputs": [], "source": [ "neighbours = {w: [n for n in adjacents(w) if n in words]\n", " for w in words}" ] }, { "cell_type": "code", "execution_count": 5, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def distance(w1, w2):\n", " return sum(1 for i in range(len(w1))\n", " if w1[i] != w2[i])" ] }, { "cell_type": "code", "execution_count": 6, "metadata": { "collapsed": true }, "outputs": [], "source": [ "# def extend(chain):\n", "# return [chain + [s] for s in neighbours[chain[-1]]\n", "# if s not in chain]" ] }, { "cell_type": "code", "execution_count": 7, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def extend(chain, closed=None):\n", " if closed:\n", " nbrs = set(neighbours[chain[-1]]) - closed\n", " else:\n", " nbrs = neighbours[chain[-1]]\n", " return [chain + [s] for s in nbrs\n", " if s not in chain]" ] }, { "cell_type": "code", "execution_count": 8, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def extend_raw(chain):\n", " nbrs = [w for w in adjacents(chain[-1]) if w in words]\n", " return [chain + [s] for s in nbrs\n", " if s not in chain]" ] }, { "cell_type": "code", "execution_count": 9, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def bfs_search(start, goal, debug=False):\n", " agenda = [[start]]\n", " finished = False\n", " while not finished and agenda:\n", " current = agenda[0]\n", " if debug:\n", " print(current)\n", " if current[-1] == goal:\n", " finished = True\n", " else:\n", " successors = extend(current)\n", " agenda = agenda[1:] + successors\n", " if finished:\n", " return current\n", " else:\n", " return None " ] }, { "cell_type": "code", "execution_count": 10, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def bfs_search_closed(start, goal, debug=False):\n", " agenda = [[start]]\n", " closed = set()\n", " finished = False\n", " while not finished and agenda:\n", " current = agenda[0]\n", " if debug:\n", " print(current)\n", " if current[-1] == goal:\n", " finished = True\n", " else:\n", " closed.add(current[-1])\n", " successors = extend(current, closed)\n", " agenda = agenda[1:] + successors\n", " if finished:\n", " return current\n", " else:\n", " return None " ] }, { "cell_type": "code", "execution_count": 11, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def dfs_search(start, goal, debug=False):\n", " agenda = [[start]]\n", " finished = False\n", " while not finished and agenda:\n", " current = agenda[0]\n", " if debug:\n", " print(current)\n", " if current[-1] == goal:\n", " finished = True\n", " else:\n", " successors = extend(current)\n", " agenda = successors + agenda[1:]\n", " if finished:\n", " return current\n", " else:\n", " return None " ] }, { "cell_type": "code", "execution_count": 12, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def astar_search(start, goal, debug=False):\n", " agenda = [(distance(start, goal), [start])]\n", " heapq.heapify(agenda)\n", " finished = False\n", " while not finished and agenda:\n", " _, current = heapq.heappop(agenda)\n", " if debug:\n", " print(current)\n", " if current[-1] == goal:\n", " finished = True\n", " else:\n", " successors = extend(current)\n", " for s in successors:\n", " heapq.heappush(agenda, (len(current) + distance(s[-1], goal) - 1, s))\n", " if finished:\n", " return current\n", " else:\n", " return None " ] }, { "cell_type": "code", "execution_count": 13, "metadata": { "collapsed": true }, "outputs": [], "source": [ "# Uses direct lookup of successors, rather than using cached neighbours in the dict\n", "def astar_search_raw(start, goal, debug=False):\n", " agenda = [(distance(start, goal), [start])]\n", " heapq.heapify(agenda)\n", " finished = False\n", " while not finished and agenda:\n", " _, current = heapq.heappop(agenda)\n", " if debug:\n", " print(current)\n", " if current[-1] == goal:\n", " finished = True\n", " else:\n", " successors = extend_raw(current) # Difference here\n", " for s in successors:\n", " heapq.heappush(agenda, (len(current) + distance(s[-1], goal) - 1, s))\n", " if finished:\n", " return current\n", " else:\n", " return None " ] }, { "cell_type": "code", "execution_count": 14, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def astar_search_closed(start, goal, debug=False):\n", " agenda = [(distance(start, goal), [start])]\n", " heapq.heapify(agenda)\n", " closed = set()\n", " finished = False\n", " while not finished and agenda:\n", " _, current = heapq.heappop(agenda)\n", " if debug:\n", " print(current)\n", " if current[-1] == goal:\n", " finished = True\n", " else:\n", " closed.add(current[-1])\n", " successors = extend(current, closed)\n", " for s in successors:\n", " heapq.heappush(agenda, (len(current) + distance(s[-1], goal) - 1, s))\n", " if finished:\n", " return current\n", " else:\n", " return None " ] }, { "cell_type": "code", "execution_count": 15, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['vice', 'dice', 'dire', 'dare', 'ware', 'wars']" ] }, "execution_count": 15, "metadata": {}, "output_type": "execute_result" } ], "source": [ "astar_search('vice', 'wars')" ] }, { "cell_type": "code", "execution_count": 16, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['vice', 'dice', 'dire', 'dare', 'ware', 'wars']" ] }, "execution_count": 16, "metadata": {}, "output_type": "execute_result" } ], "source": [ "astar_search_raw('vice', 'wars')" ] }, { "cell_type": "code", "execution_count": 17, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['boon', 'boot', 'bolt', 'belt', 'bell', 'sell']" ] }, "execution_count": 17, "metadata": {}, "output_type": "execute_result" } ], "source": [ "astar_search_raw('boon', 'sell')" ] }, { "cell_type": "code", "execution_count": 18, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "6" ] }, "execution_count": 18, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(astar_search('vice', 'wars'))" ] }, { "cell_type": "code", "execution_count": 19, "metadata": { "collapsed": true }, "outputs": [], "source": [ "# len(bfs_search('vice', 'wars'))" ] }, { "cell_type": "code", "execution_count": 20, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "6" ] }, "execution_count": 20, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(bfs_search_closed('vice', 'wars'))" ] }, { "cell_type": "code", "execution_count": 21, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "793" ] }, "execution_count": 21, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(dfs_search('vice', 'wars'))" ] }, { "cell_type": "code", "execution_count": 22, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "10000 loops, best of 3: 154 µs per loop\n" ] } ], "source": [ "%%timeit\n", "astar_search('vice', 'wars')" ] }, { "cell_type": "code", "execution_count": 23, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "100 loops, best of 3: 16.3 ms per loop\n" ] } ], "source": [ "%%timeit\n", "astar_search_raw('vice', 'wars')" ] }, { "cell_type": "code", "execution_count": 24, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "10000 loops, best of 3: 169 µs per loop\n" ] } ], "source": [ "%%timeit\n", "astar_search_closed('vice', 'wars')" ] }, { "cell_type": "code", "execution_count": 25, "metadata": { "collapsed": true }, "outputs": [], "source": [ "# %%timeit\n", "# bfs_search('vice', 'wars')" ] }, { "cell_type": "code", "execution_count": 26, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "1 loop, best of 3: 1.09 s per loop\n" ] } ], "source": [ "%%timeit\n", "bfs_search_closed('vice', 'wars')" ] }, { "cell_type": "code", "execution_count": 27, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "10 loops, best of 3: 93.1 ms per loop\n" ] } ], "source": [ "%%timeit\n", "dfs_search('vice', 'wars')" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Part 2\n", "\n", "The example shows that `jags` is reachable in four steps from `rash`. There are 11 words one step away from `rash`: \n", "`bash`, `cash`, `dash`, `gash`, `hash`, `lash`, `mash`, `rasp`, `rush`, `sash`, and `wash`. \n", "\n", "There are 47 words reachable in one or two steps from `rash`. They are `base`, `bash`, `bask`, `bass`, `bast`, `bath`, `bosh`, `bush`, `case`, `cash`, `cask`, `cast`, `dash`, `dish`, `gash`, `gasp`, `gosh`, `gush`, `hash`, `hasp`, `hath`, `hush`, `lash`, `lass`, `last`, `lath`, `lush`, `mash`, `mask`, `mass`, `mast`, `math`, `mesh`, `mush`, `push`, `ramp`, `rasp`, `ruse`, `rush`, `rusk`, `rust`, `sash`, `sass`, `tush`, `wash`, `wasp`, and `wish`.\n", "\n", "There are 180 words reachable in up to three steps from `rash`.\n", "\n", "How many words are reachable in up to ten steps from `vice`?" ] }, { "cell_type": "code", "execution_count": 28, "metadata": { "collapsed": true }, "outputs": [], "source": [ "def reachable_in(word, n, trim_extras=False):\n", " reachable = set()\n", " boundary = set([word])\n", " for i in range(n):\n", " extras = set()\n", " for w in boundary:\n", " extras.update(neighbours[w])\n", " if trim_extras:\n", " extras.difference_update(reachable)\n", " reachable.update(boundary)\n", " boundary = extras.copy()\n", " return reachable.union(extras).difference(set([word]))" ] }, { "cell_type": "code", "execution_count": 29, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['bash',\n", " 'cash',\n", " 'dash',\n", " 'gash',\n", " 'hash',\n", " 'lash',\n", " 'mash',\n", " 'sash',\n", " 'wash',\n", " 'rush',\n", " 'rasp']" ] }, "execution_count": 29, "metadata": {}, "output_type": "execute_result" } ], "source": [ "neighbours['rash']" ] }, { "cell_type": "code", "execution_count": 30, "metadata": { "scrolled": true }, "outputs": [ { "data": { "text/plain": [ "(11,\n", " '`bash`, `cash`, `dash`, `gash`, `hash`, `lash`, `mash`, `rasp`, `rush`, `sash`, `wash`')" ] }, "execution_count": 30, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('rash', 1)), ', '.join(sorted('`{}`'.format(r) for r in reachable_in('rash', 1)))" ] }, { "cell_type": "code", "execution_count": 31, "metadata": { "scrolled": true }, "outputs": [ { "data": { "text/plain": [ "(11,\n", " 'bash, cash, dash, gash, hash, lash, mash, rasp, rush, sash, wash')" ] }, "execution_count": 31, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('rash', 1)), ', '.join(sorted('{}'.format(r) for r in reachable_in('rash', 1)))" ] }, { "cell_type": "code", "execution_count": 32, "metadata": { "scrolled": true }, "outputs": [ { "data": { "text/plain": [ "(47,\n", " '`base`, `bash`, `bask`, `bass`, `bast`, `bath`, `bosh`, `bush`, `case`, `cash`, `cask`, `cast`, `dash`, `dish`, `gash`, `gasp`, `gosh`, `gush`, `hash`, `hasp`, `hath`, `hush`, `lash`, `lass`, `last`, `lath`, `lush`, `mash`, `mask`, `mass`, `mast`, `math`, `mesh`, `mush`, `push`, `ramp`, `rasp`, `ruse`, `rush`, `rusk`, `rust`, `sash`, `sass`, `tush`, `wash`, `wasp`, `wish`')" ] }, "execution_count": 32, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('rash', 2)), ', '.join(sorted('`{}`'.format(r) for r in reachable_in('rash', 2)))" ] }, { "cell_type": "code", "execution_count": 33, "metadata": { "scrolled": true }, "outputs": [ { "data": { "text/plain": [ "(47,\n", " 'base, bash, bask, bass, bast, bath, bosh, bush, case, cash, cask, cast, dash, dish, gash, gasp, gosh, gush, hash, hasp, hath, hush, lash, lass, last, lath, lush, mash, mask, mass, mast, math, mesh, mush, push, ramp, rasp, ruse, rush, rusk, rust, sash, sass, tush, wash, wasp, wish')" ] }, "execution_count": 33, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('rash', 2)), ', '.join(sorted('{}'.format(r) for r in reachable_in('rash', 2)))" ] }, { "cell_type": "code", "execution_count": 34, "metadata": { "scrolled": true }, "outputs": [ { "data": { "text/plain": [ "180" ] }, "execution_count": 34, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('rash', 3))" ] }, { "cell_type": "code", "execution_count": 35, "metadata": { "scrolled": true }, "outputs": [ { "data": { "text/plain": [ "2195" ] }, "execution_count": 35, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('rash', 10))" ] }, { "cell_type": "code", "execution_count": 36, "metadata": { "scrolled": true }, "outputs": [ { "data": { "text/plain": [ "2192" ] }, "execution_count": 36, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('vice', 10))" ] }, { "cell_type": "code", "execution_count": 37, "metadata": { "scrolled": true }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "100 loops, best of 3: 6 ms per loop\n" ] } ], "source": [ "%%timeit\n", "len(reachable_in('rash', 10))" ] }, { "cell_type": "code", "execution_count": 38, "metadata": { "scrolled": true }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "100 loops, best of 3: 2.8 ms per loop\n" ] } ], "source": [ "%%timeit\n", "len(reachable_in('rash', 10, trim_extras=True))" ] }, { "cell_type": "code", "execution_count": 39, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "2188" ] }, "execution_count": 39, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('stay', 10))" ] }, { "cell_type": "code", "execution_count": 40, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "2193" ] }, "execution_count": 40, "metadata": {}, "output_type": "execute_result" } ], "source": [ "len(reachable_in('coax', 10))" ] }, { "cell_type": "code", "execution_count": 41, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "280" ] }, "execution_count": 41, "metadata": {}, "output_type": "execute_result" } ], "source": [ "stay5 = reachable_in('stay', 4)\n", "len(stay5)" ] }, { "cell_type": "code", "execution_count": 42, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "296" ] }, "execution_count": 42, "metadata": {}, "output_type": "execute_result" } ], "source": [ "extras = set()\n", "for w in stay5:\n", " extras.update(neighbours[w])\n", "extras.difference_update(stay5)\n", "len(extras)" ] }, { "cell_type": "code", "execution_count": 43, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "'troy peck thaw bobs fist whim deed foam herd skid cell meet lens cock lean been tees cent veil glue hell hoot jeep atop whet chew crow dual keen test reed bolt coop weep went dell lent pens prop leek chop pock knob bend dent gent bloc pets whom brew gout brat clue sacs nets gram wiry blur gees crop glib bets thin knit dram hair jeez soon sort leaf prim hemp deep yews loan bows wees rock newt mock baas leak twin sots bogs sick geed yock peel airs crew know beet pier foot melt less prep toad prom pews brow grad pees suet sued prod lees dock frog term tent sack root stay chin feet twit tram pert coat reel floe deem teem need boss moat book bias lock said best loam goop spec boon bras boys grey pelt nest jets well perk mead heel tens fled czar trap mewl brad teen very belt boom chit pent shes soil next toot crab jock foul held heft help coot berm moan char boot omit hock unit akin load boob lead beep plus sewn bees chow knot vial bled drag bell doer pest saws peed news aloe goad moot tout text tell fret gets chip rent whir bout coup pegs flea poop room peek wets hews grow dyer whit sics self than club week peep clef beef poor step brag rood vent sill legs send shoo bops sits flue emit stem grab shoe eery leap whip door yens heed felt yous quit meek bran teed moor veep loot geek bier goat weed flee pout skis blue yell yeps reek trig feed draw rend soft bent crag mews sues leis fees drab mean peps suck dial fest vets lets sped keep jell beck boos fell pled sows'" ] }, "execution_count": 43, "metadata": {}, "output_type": "execute_result" } ], "source": [ "' '.join(extras)" ] }, { "cell_type": "code", "execution_count": 44, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['coax', 'coat', 'boat', 'boar', 'soar', 'star', 'stay']" ] }, "execution_count": 44, "metadata": {}, "output_type": "execute_result" } ], "source": [ "astar_search('coax', 'stay')" ] }, { "cell_type": "code", "execution_count": 45, "metadata": {}, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "CPU times: user 2.28 s, sys: 4 ms, total: 2.29 s\n", "Wall time: 2.29 s\n" ] }, { "data": { "text/plain": [ "['coax', 'coat', 'boat', 'boar', 'soar', 'star', 'stay']" ] }, "execution_count": 45, "metadata": {}, "output_type": "execute_result" } ], "source": [ "%time bfs_search_closed('coax', 'stay')" ] }, { "cell_type": "code", "execution_count": 46, "metadata": { "collapsed": true }, "outputs": [], "source": [ "# %time bfs_search('coax', 'stay')" ] }, { "cell_type": "code", "execution_count": 47, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "['czar', 'tzar', 'tear', 'sear', 'star', 'stay']" ] }, "execution_count": 47, "metadata": {}, "output_type": "execute_result" } ], "source": [ "astar_search('czar', 'stay')" ] }, { "cell_type": "code", "execution_count": 48, "metadata": { "collapsed": true }, "outputs": [], "source": [ "# %time bfs_search('czar', 'stay')" ] }, { "cell_type": "code", "execution_count": 49, "metadata": { "collapsed": true }, "outputs": [], "source": [ "# %time bfs_search('coax', 'stay')" ] }, { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": true }, "outputs": [], "source": [] } ], "metadata": { "kernelspec": { "display_name": "Python 3", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.5.2+" } }, "nbformat": 4, "nbformat_minor": 2 }