Minor changes
[ou-summer-of-code-2017.git] / 09-resolving-the-bill / subsequence.ipynb
1 {
2 "cells": [
3 {
4 "cell_type": "markdown",
5 "metadata": {},
6 "source": [
7 "# Subsequence strings\n",
8 "\n",
9 "Given two strings `a` and `b`, is `a` a subsequence of `b`?\n",
10 "\n",
11 "For example,\n",
12 "Given:\n",
13 "a = \"aabcc\",\n",
14 "b = \"dabaabcacb\",\n",
15 "\n",
16 "return True : dAbAaBCaCb\n",
17 "\n"
18 ]
19 },
20 {
21 "cell_type": "code",
22 "execution_count": 1,
23 "metadata": {
24 "collapsed": true
25 },
26 "outputs": [],
27 "source": [
28 "s1 = \"aabcc\"\n",
29 "s2t = \"dabaabcacb\"\n",
30 "s2f = \"dabacc\"\n",
31 "\n",
32 "s2 = s2t"
33 ]
34 },
35 {
36 "cell_type": "markdown",
37 "metadata": {},
38 "source": [
39 "`dp_table[i, j]` is True if first `i` characters of `s1` can be found in first `j` characters of `s2`."
40 ]
41 },
42 {
43 "cell_type": "code",
44 "execution_count": 2,
45 "metadata": {
46 "scrolled": true
47 },
48 "outputs": [
49 {
50 "data": {
51 "text/plain": [
52 "{(0, 0): False,\n",
53 " (0, 1): False,\n",
54 " (0, 2): False,\n",
55 " (0, 3): False,\n",
56 " (0, 4): False,\n",
57 " (0, 5): False,\n",
58 " (0, 6): False,\n",
59 " (0, 7): False,\n",
60 " (0, 8): False,\n",
61 " (0, 9): False,\n",
62 " (0, 10): False,\n",
63 " (1, 0): False,\n",
64 " (1, 1): False,\n",
65 " (1, 2): False,\n",
66 " (1, 3): False,\n",
67 " (1, 4): False,\n",
68 " (1, 5): False,\n",
69 " (1, 6): False,\n",
70 " (1, 7): False,\n",
71 " (1, 8): False,\n",
72 " (1, 9): False,\n",
73 " (1, 10): False,\n",
74 " (2, 0): False,\n",
75 " (2, 1): False,\n",
76 " (2, 2): False,\n",
77 " (2, 3): False,\n",
78 " (2, 4): False,\n",
79 " (2, 5): False,\n",
80 " (2, 6): False,\n",
81 " (2, 7): False,\n",
82 " (2, 8): False,\n",
83 " (2, 9): False,\n",
84 " (2, 10): False,\n",
85 " (3, 0): False,\n",
86 " (3, 1): False,\n",
87 " (3, 2): False,\n",
88 " (3, 3): False,\n",
89 " (3, 4): False,\n",
90 " (3, 5): False,\n",
91 " (3, 6): False,\n",
92 " (3, 7): False,\n",
93 " (3, 8): False,\n",
94 " (3, 9): False,\n",
95 " (3, 10): False,\n",
96 " (4, 0): False,\n",
97 " (4, 1): False,\n",
98 " (4, 2): False,\n",
99 " (4, 3): False,\n",
100 " (4, 4): False,\n",
101 " (4, 5): False,\n",
102 " (4, 6): False,\n",
103 " (4, 7): False,\n",
104 " (4, 8): False,\n",
105 " (4, 9): False,\n",
106 " (4, 10): False,\n",
107 " (5, 0): False,\n",
108 " (5, 1): False,\n",
109 " (5, 2): False,\n",
110 " (5, 3): False,\n",
111 " (5, 4): False,\n",
112 " (5, 5): False,\n",
113 " (5, 6): False,\n",
114 " (5, 7): False,\n",
115 " (5, 8): False,\n",
116 " (5, 9): False,\n",
117 " (5, 10): False}"
118 ]
119 },
120 "execution_count": 2,
121 "metadata": {},
122 "output_type": "execute_result"
123 }
124 ],
125 "source": [
126 "dp_table = {(i, j): False\n",
127 " for i in range(len(s1)+1)\n",
128 " for j in range(len(s2)+1)}\n",
129 "dp_table"
130 ]
131 },
132 {
133 "cell_type": "code",
134 "execution_count": 3,
135 "metadata": {
136 "collapsed": true
137 },
138 "outputs": [],
139 "source": [
140 "def show_table(table):\n",
141 " return '\\n'.join(\n",
142 " ' '.join(str(table[i, j])[0] for j in sorted(set([k[1] for k in table])))\n",
143 " for i in sorted(set([k[0] for k in table]))) "
144 ]
145 },
146 {
147 "cell_type": "code",
148 "execution_count": 4,
149 "metadata": {},
150 "outputs": [
151 {
152 "name": "stdout",
153 "output_type": "stream",
154 "text": [
155 "F F F F F F F F F F F\n",
156 "F F F F F F F F F F F\n",
157 "F F F F F F F F F F F\n",
158 "F F F F F F F F F F F\n",
159 "F F F F F F F F F F F\n",
160 "F F F F F F F F F F F\n"
161 ]
162 }
163 ],
164 "source": [
165 "print(show_table(dp_table))"
166 ]
167 },
168 {
169 "cell_type": "code",
170 "execution_count": 5,
171 "metadata": {},
172 "outputs": [
173 {
174 "name": "stdout",
175 "output_type": "stream",
176 "text": [
177 "aaaa aaababb\n",
178 "aa 0 0 ! ! True\n",
179 "aa 0 1 ! ! True\n",
180 "aa 0 2 ! ! True\n",
181 "aa 0 3 ! ! True\n",
182 "aa 0 4 ! ! True\n",
183 "aa 0 5 ! ! True\n",
184 "aa 0 6 ! ! True\n",
185 "aa 0 7 ! ! True\n",
186 "s1 1 1 a a True\n",
187 "s2 1 2 a a True\n",
188 "s1 1 2 a a True\n",
189 "s2 1 3 a a True\n",
190 "s1 1 3 a a True\n",
191 "s2 1 4 a b True\n",
192 "s2 1 5 a a True\n",
193 "s1 1 5 a a True\n",
194 "s2 1 6 a b True\n",
195 "s2 1 7 a b True\n",
196 "s1 2 2 a a True\n",
197 "s2 2 3 a a True\n",
198 "s1 2 3 a a True\n",
199 "s2 2 4 a b True\n",
200 "s2 2 5 a a True\n",
201 "s1 2 5 a a True\n",
202 "s2 2 6 a b True\n",
203 "s2 2 7 a b True\n",
204 "s1 3 3 a a True\n",
205 "s2 3 4 a b True\n",
206 "s2 3 5 a a True\n",
207 "s1 3 5 a a True\n",
208 "s2 3 6 a b True\n",
209 "s2 3 7 a b True\n",
210 "xx 4 4 a b False\n",
211 "s1 4 5 a a True\n",
212 "s2 4 6 a b True\n",
213 "s2 4 7 a b True\n",
214 "T T T T T T T T\n",
215 "F T T T T T T T\n",
216 "F F T T T T T T\n",
217 "F F F T T T T T\n",
218 "F F F F F T T T\n"
219 ]
220 },
221 {
222 "data": {
223 "text/plain": [
224 "{(1, 1): (0, 0, 'a', 's1'),\n",
225 " (1, 2): (0, 1, 'a', 's1'),\n",
226 " (1, 3): (0, 2, 'a', 's1'),\n",
227 " (1, 4): (1, 3, 'b', 's2'),\n",
228 " (1, 5): (0, 4, 'a', 's1'),\n",
229 " (1, 6): (1, 5, 'b', 's2'),\n",
230 " (1, 7): (1, 6, 'b', 's2'),\n",
231 " (2, 2): (1, 1, 'a', 's1'),\n",
232 " (2, 3): (1, 2, 'a', 's1'),\n",
233 " (2, 4): (2, 3, 'b', 's2'),\n",
234 " (2, 5): (1, 4, 'a', 's1'),\n",
235 " (2, 6): (2, 5, 'b', 's2'),\n",
236 " (2, 7): (2, 6, 'b', 's2'),\n",
237 " (3, 3): (2, 2, 'a', 's1'),\n",
238 " (3, 4): (3, 3, 'b', 's2'),\n",
239 " (3, 5): (2, 4, 'a', 's1'),\n",
240 " (3, 6): (3, 5, 'b', 's2'),\n",
241 " (3, 7): (3, 6, 'b', 's2'),\n",
242 " (4, 5): (3, 4, 'a', 's1'),\n",
243 " (4, 6): (4, 5, 'b', 's2'),\n",
244 " (4, 7): (4, 6, 'b', 's2')}"
245 ]
246 },
247 "execution_count": 5,
248 "metadata": {},
249 "output_type": "execute_result"
250 }
251 ],
252 "source": [
253 "s2 = s2f\n",
254 "\n",
255 "s1 = 'aaaa'\n",
256 "s2 = 'aaababb'\n",
257 "\n",
258 "print(s1, s2)\n",
259 "\n",
260 "dp_table = {(i, j): False\n",
261 " for i in range(len(s1)+1)\n",
262 " for j in range(len(s2)+1)}\n",
263 "\n",
264 "backpointers = {}\n",
265 "\n",
266 "for i in range(len(s1)+1):\n",
267 " for j in range(i, len(s2)+1):\n",
268 " if i == 0 or j == 0:\n",
269 " dp_table[i, j] = True\n",
270 " print('aa', i, j, '!', '!', dp_table[i, j])\n",
271 " else:\n",
272 " # extend by character from s2\n",
273 " if dp_table[i, j-1]:\n",
274 " dp_table[i, j] = True\n",
275 " backpointers[i, j] = (i, j-1, s2[j-1], 's2')\n",
276 " print('s2', i, j, s1[i-1], s2[j-1], dp_table[i, j]) \n",
277 " # extend by character from s1\n",
278 " if dp_table[i-1, j-1] and s1[i-1] == s2[j-1]:\n",
279 " dp_table[i, j] = True\n",
280 " backpointers[i, j] = (i-1, j-1, s1[i-1], 's1') \n",
281 " print('s1', i, j, s1[i-1], s2[j-1], dp_table[i, j])\n",
282 " if not dp_table[i, j]:\n",
283 " print('xx', i, j, s1[i-1], s2[j-1], dp_table[i, j])\n",
284 "\n",
285 "print(show_table(dp_table))\n",
286 "backpointers"
287 ]
288 },
289 {
290 "cell_type": "code",
291 "execution_count": 13,
292 "metadata": {
293 "collapsed": true
294 },
295 "outputs": [],
296 "source": [
297 "def show_backtrace(bps):\n",
298 " i = max([0] + [k[0] for k in bps])\n",
299 " j = max([0] + [k[1] for k in bps])\n",
300 " chars = ''\n",
301 " if (i, j) in bps:\n",
302 " while i != 0 and j != 0:\n",
303 " if bps[i, j][3] == 's1':\n",
304 " chars += bps[i, j][2].upper()\n",
305 " else:\n",
306 " chars += bps[i, j][2]\n",
307 " i, j = bps[i, j][0], bps[i, j][1] \n",
308 " return ''.join(list(reversed(chars)))\n",
309 " else:\n",
310 " return ''"
311 ]
312 },
313 {
314 "cell_type": "code",
315 "execution_count": 7,
316 "metadata": {},
317 "outputs": [
318 {
319 "data": {
320 "text/plain": [
321 "'AAAbAbb'"
322 ]
323 },
324 "execution_count": 7,
325 "metadata": {},
326 "output_type": "execute_result"
327 }
328 ],
329 "source": [
330 "show_backtrace(backpointers)"
331 ]
332 },
333 {
334 "cell_type": "code",
335 "execution_count": 28,
336 "metadata": {},
337 "outputs": [
338 {
339 "name": "stdout",
340 "output_type": "stream",
341 "text": [
342 "aa 0 0 ! ! True\n",
343 "aa 0 1 ! ! True\n",
344 "aa 0 2 ! ! True\n",
345 "aa 0 3 ! ! True\n",
346 "aa 0 4 ! ! True\n",
347 "aa 0 5 ! ! True\n",
348 "aa 0 6 ! ! True\n",
349 "aa 0 7 ! ! True\n",
350 "aa 0 8 ! ! True\n",
351 "aa 0 9 ! ! True\n",
352 "aa 0 10 ! ! True\n",
353 "xx 1 1 a d False\n",
354 "s1 1 2 a a True\n",
355 "s2 1 3 a b True\n",
356 "s2 1 4 a a True\n",
357 "s1 1 4 a a True\n",
358 "s2 1 5 a a True\n",
359 "s1 1 5 a a True\n",
360 "s2 1 6 a b True\n",
361 "s2 1 7 a c True\n",
362 "s2 1 8 a a True\n",
363 "s1 1 8 a a True\n",
364 "s2 1 9 a c True\n",
365 "s2 1 10 a b True\n",
366 "xx 2 2 a a False\n",
367 "xx 2 3 a b False\n",
368 "s1 2 4 a a True\n",
369 "s2 2 5 a a True\n",
370 "s1 2 5 a a True\n",
371 "s2 2 6 a b True\n",
372 "s2 2 7 a c True\n",
373 "s2 2 8 a a True\n",
374 "s1 2 8 a a True\n",
375 "s2 2 9 a c True\n",
376 "s2 2 10 a b True\n",
377 "xx 3 3 a b False\n",
378 "xx 3 4 a a False\n",
379 "s1 3 5 a a True\n",
380 "s2 3 6 a b True\n",
381 "s2 3 7 a c True\n",
382 "s2 3 8 a a True\n",
383 "s1 3 8 a a True\n",
384 "s2 3 9 a c True\n",
385 "s2 3 10 a b True\n",
386 "xx 4 4 a a False\n",
387 "xx 4 5 a a False\n",
388 "xx 4 6 a b False\n",
389 "xx 4 7 a c False\n",
390 "s1 4 8 a a True\n",
391 "s2 4 9 a c True\n",
392 "s2 4 10 a b True\n"
393 ]
394 },
395 {
396 "data": {
397 "text/plain": [
398 "True"
399 ]
400 },
401 "execution_count": 28,
402 "metadata": {},
403 "output_type": "execute_result"
404 }
405 ],
406 "source": [
407 "is_subseq(s1, s2t, debug=True)"
408 ]
409 },
410 {
411 "cell_type": "code",
412 "execution_count": 27,
413 "metadata": {
414 "collapsed": true
415 },
416 "outputs": [],
417 "source": [
418 "def is_subseq(seq1, seq2, return_backpointers=False, return_table=False, debug=False):\n",
419 " \"\"\"Return true if seq1 is a subsequence of seq2.\n",
420 " If return_backpointers, also return the set of backpointers to\n",
421 " reconstruct the subsequence\"\"\"\n",
422 " \n",
423 " # dp_table[i, j] is True if first i characters of seq1 can\n",
424 " # be found in the first j characters of seq2\n",
425 " \n",
426 " dp_table = {(i, j): False\n",
427 " for i in range(len(seq1)+1)\n",
428 " for j in range(len(seq2)+1)}\n",
429 "\n",
430 " backpointers = {}\n",
431 " \n",
432 " for i in range(len(seq1)+1):\n",
433 " for j in range(i, len(seq2)+1):\n",
434 " if i == 0 or j == 0:\n",
435 " dp_table[i, j] = True\n",
436 " if debug: print('aa', i, j, '!', '!', dp_table[i, j])\n",
437 " else:\n",
438 " # extend by character from s2\n",
439 " if dp_table[i, j-1]:\n",
440 " dp_table[i, j] = True\n",
441 " backpointers[i, j] = (i, j-1, seq2[j-1], 's2')\n",
442 " if debug: print('s2', i, j, seq1[i-1], seq2[j-1], dp_table[i, j]) \n",
443 " # extend by character from s1\n",
444 " if dp_table[i-1, j-1] and seq1[i-1] == seq2[j-1]:\n",
445 " dp_table[i, j] = True\n",
446 " backpointers[i, j] = (i-1, j-1, seq1[i-1], 's1') \n",
447 " if debug: print('s1', i, j, seq1[i-1], seq2[j-1], dp_table[i, j])\n",
448 " if not dp_table[i, j]:\n",
449 " if debug: print('xx', i, j, seq1[i-1], seq2[j-1], dp_table[i, j]) \n",
450 " \n",
451 "# if return_backpointers:\n",
452 "# return dp_table[len(seq1), len(seq2)], backpointers\n",
453 "# else:\n",
454 "# return dp_table[len(seq1), len(seq2)]\n",
455 " \n",
456 " if return_backpointers or return_table:\n",
457 " retval = [dp_table[len(seq1), len(seq2)]]\n",
458 " if return_backpointers:\n",
459 " retval += [backpointers]\n",
460 " if return_table:\n",
461 " retval += [dp_table]\n",
462 " return tuple(retval)\n",
463 " else:\n",
464 " return dp_table[len(seq1), len(seq2)]"
465 ]
466 },
467 {
468 "cell_type": "code",
469 "execution_count": 37,
470 "metadata": {
471 "collapsed": true
472 },
473 "outputs": [],
474 "source": [
475 "def show_annotated_table(table, bps):\n",
476 " return '\\n'.join(' '.join('.' if (i, j) not in bps else bps[i, j][2] if table[i, j] else '.' for j in sorted(set([k[1] for k in table])))\n",
477 " for i in sorted(set([k[0] for k in table])))"
478 ]
479 },
480 {
481 "cell_type": "code",
482 "execution_count": 29,
483 "metadata": {},
484 "outputs": [
485 {
486 "data": {
487 "text/plain": [
488 "True"
489 ]
490 },
491 "execution_count": 29,
492 "metadata": {},
493 "output_type": "execute_result"
494 }
495 ],
496 "source": [
497 "tf, bps, tb = is_subseq(s1, s2t, return_backpointers=True, return_table=True)\n",
498 "tf"
499 ]
500 },
501 {
502 "cell_type": "code",
503 "execution_count": 20,
504 "metadata": {},
505 "outputs": [
506 {
507 "data": {
508 "text/plain": [
509 "'AbAAbcAcb'"
510 ]
511 },
512 "execution_count": 20,
513 "metadata": {},
514 "output_type": "execute_result"
515 }
516 ],
517 "source": [
518 "show_backtrace(bps)"
519 ]
520 },
521 {
522 "cell_type": "code",
523 "execution_count": 32,
524 "metadata": {},
525 "outputs": [
526 {
527 "name": "stdout",
528 "output_type": "stream",
529 "text": [
530 "T T T T T T T T T T T\n",
531 "F F T T T T T T T T T\n",
532 "F F F F T T T T T T T\n",
533 "F F F F F T T T T T T\n",
534 "F F F F F F F F T T T\n"
535 ]
536 }
537 ],
538 "source": [
539 "print(show_table(tb))"
540 ]
541 },
542 {
543 "cell_type": "code",
544 "execution_count": 38,
545 "metadata": {},
546 "outputs": [
547 {
548 "name": "stdout",
549 "output_type": "stream",
550 "text": [
551 ". . . . . . . . . . .\n",
552 ". . a b a a b c a c b\n",
553 ". . . . a a b c a c b\n",
554 ". . . . . a b c a c b\n",
555 ". . . . . . . . a c b\n"
556 ]
557 }
558 ],
559 "source": [
560 "print(show_annotated_table(tb, bps))"
561 ]
562 },
563 {
564 "cell_type": "code",
565 "execution_count": 21,
566 "metadata": {},
567 "outputs": [
568 {
569 "data": {
570 "text/plain": [
571 "False"
572 ]
573 },
574 "execution_count": 21,
575 "metadata": {},
576 "output_type": "execute_result"
577 }
578 ],
579 "source": [
580 "len(show_backtrace(bps)) == len(s2t)"
581 ]
582 },
583 {
584 "cell_type": "code",
585 "execution_count": 24,
586 "metadata": {},
587 "outputs": [
588 {
589 "data": {
590 "text/plain": [
591 "('aaaa', 'dabaabcacb')"
592 ]
593 },
594 "execution_count": 24,
595 "metadata": {},
596 "output_type": "execute_result"
597 }
598 ],
599 "source": [
600 "s1, s2t"
601 ]
602 },
603 {
604 "cell_type": "code",
605 "execution_count": 23,
606 "metadata": {},
607 "outputs": [
608 {
609 "data": {
610 "text/plain": [
611 "{(1, 2): (0, 1, 'a', 's1'),\n",
612 " (1, 3): (1, 2, 'b', 's2'),\n",
613 " (1, 4): (0, 3, 'a', 's1'),\n",
614 " (1, 5): (0, 4, 'a', 's1'),\n",
615 " (1, 6): (1, 5, 'b', 's2'),\n",
616 " (1, 7): (1, 6, 'c', 's2'),\n",
617 " (1, 8): (0, 7, 'a', 's1'),\n",
618 " (1, 9): (1, 8, 'c', 's2'),\n",
619 " (1, 10): (1, 9, 'b', 's2'),\n",
620 " (2, 4): (1, 3, 'a', 's1'),\n",
621 " (2, 5): (1, 4, 'a', 's1'),\n",
622 " (2, 6): (2, 5, 'b', 's2'),\n",
623 " (2, 7): (2, 6, 'c', 's2'),\n",
624 " (2, 8): (1, 7, 'a', 's1'),\n",
625 " (2, 9): (2, 8, 'c', 's2'),\n",
626 " (2, 10): (2, 9, 'b', 's2'),\n",
627 " (3, 5): (2, 4, 'a', 's1'),\n",
628 " (3, 6): (3, 5, 'b', 's2'),\n",
629 " (3, 7): (3, 6, 'c', 's2'),\n",
630 " (3, 8): (2, 7, 'a', 's1'),\n",
631 " (3, 9): (3, 8, 'c', 's2'),\n",
632 " (3, 10): (3, 9, 'b', 's2'),\n",
633 " (4, 8): (3, 7, 'a', 's1'),\n",
634 " (4, 9): (4, 8, 'c', 's2'),\n",
635 " (4, 10): (4, 9, 'b', 's2')}"
636 ]
637 },
638 "execution_count": 23,
639 "metadata": {},
640 "output_type": "execute_result"
641 }
642 ],
643 "source": [
644 "bps"
645 ]
646 },
647 {
648 "cell_type": "code",
649 "execution_count": null,
650 "metadata": {},
651 "outputs": [],
652 "source": [
653 "is_subseq(s1, s2f)"
654 ]
655 },
656 {
657 "cell_type": "code",
658 "execution_count": null,
659 "metadata": {},
660 "outputs": [],
661 "source": [
662 "is_subseq('aaaa', 'aaababb', return_backpointers=True, debug=True)"
663 ]
664 },
665 {
666 "cell_type": "code",
667 "execution_count": null,
668 "metadata": {
669 "collapsed": true
670 },
671 "outputs": [],
672 "source": []
673 }
674 ],
675 "metadata": {
676 "kernelspec": {
677 "display_name": "Python 3",
678 "language": "python",
679 "name": "python3"
680 },
681 "language_info": {
682 "codemirror_mode": {
683 "name": "ipython",
684 "version": 3
685 },
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