-
Notifications
You must be signed in to change notification settings - Fork 3
/
SwissLadderGenerator.cpp
598 lines (492 loc) · 19.1 KB
/
SwissLadderGenerator.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
/*
* This is QTournament, a badminton tournament management program.
* Copyright (C) 2014 - 2019 Volker Knollmann
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "SwissLadderGenerator.h"
using namespace std;
namespace QTournament
{
SwissLadderGenerator::SwissLadderGenerator(const std::vector<int>& _ranking, const std::vector<std::tuple<int, int> >& _pastMatches)
:ranking{_ranking}, pastMatches{_pastMatches}, nPairs{_ranking.size()}
{
// no consistency checks here (e.g., do the PlayerPairIDs
// in _ranking match those in _pastMatches). Just make sure that
// ranking is not empty
if (ranking.empty())
{
throw std::invalid_argument("Empty ranking in SwissLadderGenerator!");
}
// calculate the number of matches per round
matchesPerRound = ((nPairs % 2) == 0) ? nPairs / 2 : (nPairs - 1) / 2;
// determine the number of rounds that have been played
roundsPlayed = pastMatches.size() / matchesPerRound;
// cross-check to ensure that the size of pastMatches is consistent
if ((roundsPlayed * matchesPerRound) != pastMatches.size())
{
throw std::invalid_argument("SwissLadderGenerator: inconsistent size of list of past matches");
}
// count the number of matches that each player already has played
for (const std::tuple<int, int>& m : pastMatches)
{
int pp1Id = get<0>(m);
int pp2Id = get<1>(m);
int& ref1 = matchCount[pp1Id];
++ref1;
int& ref2 = matchCount[pp2Id];
++ref2;
}
}
//----------------------------------------------------------------------------
int SwissLadderGenerator::getNextMatches(vector<std::tuple<int, int>>& resultVector)
{
//
// a few status variables for the generator
//
// is there another round at all?
int maxRounds = ((nPairs % 2) == 0) ? nPairs - 1 : nPairs;
if (maxRounds == roundsPlayed) return NO_MORE_ROUNDS; // no more rounds
// do we need a deadlock prevention check?
// This check is necessary when generating the matches
// for the round "nPairs - 3" (or "maxRounds - 2") in order to prevent
// deadlock AFTER playing that round
int nextRound = roundsPlayed + 1;
bool needsDeadlockPrevention = (nextRound == (maxRounds - 2));
// the rank of the player that has a bye
// in the next round. Is initialized to
// "one behind the last rank"
int curByeRank = nPairs;
//
// The generator itself
//
while (true)
{
// in case we start all over again because we couldn't
// find a solution, clear all previous solution fragments
resultVector.clear();
// get the list of effective players for
// the next round. remove one player (bye)
// if necessary
std::vector<int> ppList;
tie(curByeRank, ppList) = getEffectivePlayerList(curByeRank);
if (ppList.empty())
{
return DEADLOCK;
}
size_t effPairCount = ppList.size();
// prepare a list of already "used" ranks for next matches
std::vector<int> usedRanks;
// keep a list of "isRankUsed"-flags. This is redundant to
// the usedRanks-list, but makes some operations easier
std::vector<bool> isRankUsed;
for (size_t i=0; i < effPairCount; ++i) isRankUsed.push_back(false);
// start building new player combinations. Follow the approach
// "first against second", "third against fourth", etc. but avoid
// playing the same match twice.
//
// the algorithm uses two indices: one for the first player, the
// other one for the second player.
int pair1Rank = 0;
int minPair2Rank = 1;
bool foundSolution = false;
while(usedRanks.size() != effPairCount)
{
// determine the smallest unused player rank
if (pair1Rank < 0)
{
pair1Rank = getNextUnusedRank(isRankUsed, 0);
minPair2Rank = pair1Rank + 1;
}
// is there a possible other pair that results
// in a unique match?
int pair2Rank = findOpponentRank(pair1Rank, minPair2Rank, isRankUsed, ppList);
bool foundMatch = (pair2Rank > 0);
if (foundMatch)
{
// we found a unique match
//
// ==> store it
int pair1Id = ppList[pair1Rank];
int pair2Id = ppList[pair2Rank];
resultVector.push_back(make_tuple(pair1Id, pair2Id));
usedRanks.push_back(pair1Rank);
usedRanks.push_back(pair2Rank);
isRankUsed[pair1Rank] = true;
isRankUsed[pair2Rank] = true;
// set pair1Rank to -1 as an indication to start
// over with a fresh pair1Rank in the next iteration
pair1Rank = -1;
}
// Check for deadlocks. The conditions are:
// * curByeRank < 1 (-1 = no byes, even number of players; 0 = already used the top player for a bye)
// * no match found for player at rank 0
//
if ((curByeRank < 1) && (!foundMatch) && (pair1Rank == 0))
{
resultVector.clear();
return DEADLOCK;
}
// if we couldn't find a match for the player
// at rank 0 and have not yet exhausted all bye
// options, continue with another bye selection
if ((curByeRank > 0) && (!foundMatch) && (pair1Rank == 0))
{
break;
}
// perform the deadlock prevention check
// if we just completed the set of matches and
// if the deadlock prevention check is necessary
bool deadlockCheckTriggered = false;
if (needsDeadlockPrevention && (usedRanks.size() == ppList.size()))
{
deadlockCheckTriggered = matchSelectionCausesDeadlock(resultVector);
}
// if we couldn't find a match for a player
// at a rank > 0, undo the last match selection
// and continue with the match search for the
// previous pair1Rank
//
// we also undo the previous match selection if
// the deadlock check resulted in a "yes"
if (deadlockCheckTriggered || ((!foundMatch && (pair1Rank > 0))))
{
resultVector.pop_back();
pair2Rank = usedRanks.back();
usedRanks.pop_back();
pair1Rank = usedRanks.back();
usedRanks.pop_back();
isRankUsed[pair1Rank] = false;
isRankUsed[pair2Rank] = false;
minPair2Rank = pair2Rank + 1;
}
// check if we were able to find a full set of matches
foundSolution = (foundMatch && (usedRanks.size() == effPairCount));
}
// if we returned from the inner while loops with a full solution,
// we're done. Otherwise, we need to continue with the outmost while loop
// and a new bye selection
if (foundSolution) break;
}
return SOLUTION_FOUND;
}
//----------------------------------------------------------------------------
bool SwissLadderGenerator::hasMatchBeenPlayed(int pair1Id, int pair2Id) const
{
std::tuple<int, int> regular{pair1Id, pair2Id};
std::tuple<int, int> swapped{pair2Id, pair1Id};
auto it = find_if(pastMatches.cbegin(), pastMatches.cend(), [&](const std::tuple<int, int>& m) {
if (m == regular) return true;
return (m == swapped);
});
return (it != pastMatches.cend());
}
//----------------------------------------------------------------------------
pair<int, std::vector<int>> SwissLadderGenerator::getEffectivePlayerList(int curByeRank)
{
// if the number of pairs is even, all pairs participate in the next round
if ((nPairs % 2) == 0)
{
return make_pair(-1, ranking);
}
// we have an odd number of players.
//
// find the next player that has a bye, starting with
// curByeRank - 1
int nextByeRank = curByeRank -1;
while (nextByeRank >= 0)
{
int ppId = ranking[nextByeRank];
int nRounds = matchCount[ppId];
// if the player has participated in all rounds
// so far, this player will get the next bye
if (nRounds == roundsPlayed)
{
// create a copy of the ranking
std::vector<int> ppList = ranking;
// remove the player pair at nextByeRank
ppList.erase(ppList.begin() + nextByeRank);
// return the list and the erased rank
return make_pair(nextByeRank, ppList);
}
// the player already had a bye, check
// the next one
--nextByeRank;
}
// we couldn't find a bye player, that's weird and
// should not happen
return make_pair(-1, std::vector<int>{});
}
//----------------------------------------------------------------------------
int SwissLadderGenerator::getNextUnusedRank(const std::vector<bool>& isRankUsed, int minRank) const
{
size_t rank = minRank;
while (rank < isRankUsed.size())
{
if (isRankUsed[rank] == false) return rank;
++rank;
}
return -1;
}
//----------------------------------------------------------------------------
int SwissLadderGenerator::findOpponentRank(int pair1Rank, int minPair2Rank, const std::vector<bool>& isRankUsed, const std::vector<int> effPairList) const
{
if ((pair1Rank < 0) || (pair1Rank > (effPairList.size() - 2))) return -1;
if ((minPair2Rank <= pair1Rank) || (minPair2Rank > (effPairList.size() - 1))) return -1;
int pair1Id = effPairList[pair1Rank];
// keep the first pair fix while searching for
// a second pair that results in a unique match
int pair2Rank = minPair2Rank;
while (pair2Rank < effPairList.size())
{
// find the next unused rank
if (isRankUsed[pair2Rank])
{
++pair2Rank;
continue;
}
int pair2Id = effPairList[pair2Rank];
if (hasMatchBeenPlayed(pair1Id, pair2Id))
{
++pair2Rank;
continue;
}
return pair2Rank;
}
return -1;
}
//----------------------------------------------------------------------------
bool SwissLadderGenerator::matchSelectionCausesDeadlock(const std::vector<std::tuple<int, int>>& nextMatches)
{
// check whether the selection of next matches causes
// a deadlock after playing those played matches in the next
// round
// if we have more than 20 players, we do not perform
// this check because the computation might take too long.
//
// in this case we simply assume that the match selection
// is valid and we rely on the deadlock detection in the
// match generator.
if (ranking.size() > 20) return false;
// Algorithm:
//
// Step 1: determine all matches for this category (means: all player pair combinations)
// Step 2: subtract what has been played in the previous rounds (pastMatches)
// Step 3: subtract what is to be played in the next round (nextMatches)
// Step 4: check if the remaining matches allow for at least one more round
//
// Do steps 1 and 2 only once to avoid too many computations
if (remainingMatches.empty())
{
//
// Step 1: determine all matches and store them in "remainingMatches"
//
for (size_t idxFirst = 0; idxFirst < (ranking.size() - 1); ++idxFirst)
{
int idFirst = ranking[idxFirst];
for (size_t idxSecond = idxFirst + 1; idxSecond < ranking.size(); ++idxSecond)
{
int idSecond = ranking[idxSecond];
remainingMatches.push_back(make_tuple(idFirst, idSecond));
}
}
//
// Step 2: subtract already played matches
//
for (tuple<int, int>& m : pastMatches)
{
std::tuple<int, int> swapped = make_tuple(get<1>(m), get<0>(m));
auto it = find(remainingMatches.begin(), remainingMatches.end(), m);
if (it == remainingMatches.end())
{
it = find(remainingMatches.begin(), remainingMatches.end(), swapped);
}
if (it != remainingMatches.end())
{
remainingMatches.erase(it);
}
}
}
//
// Step 3: subtract next matches
//
std::vector<std::tuple<int, int>> remain = remainingMatches;
for (const std::tuple<int, int>& m : nextMatches)
{
std::tuple<int, int> swapped = make_tuple(get<1>(m), get<0>(m));
auto it = find(remain.begin(), remain.end(), m);
if (it == remain.end())
{
it = find(remain.begin(), remain.end(), swapped);
}
if (it != remain.end())
{
remain.erase(it);
}
}
//
// Step 4: check if we can create at least one more round from the
// remaining matches
//
return !(canBuildAnotherRound(remain, nextMatches));
}
//----------------------------------------------------------------------------
bool SwissLadderGenerator::canBuildAnotherRound(const std::vector<std::tuple<int, int> >& remain, const std::vector<std::tuple<int, int> >& nextMatches) const
{
// a list of indices to matchSet that make up a
// match combination for the next round
std::vector<int> usedMatchSequence;
// a list of flags that tags each entry in matchSet as used or not
std::vector<bool> isMatchUsed;
for (size_t i=0; i < remain.size(); ++i) isMatchUsed.push_back(false);
// calculate the number of matches for a round
size_t requiredMatchCount = ((ranking.size() % 2) == 0) ? ranking.size() / 2 : (ranking.size() - 1) / 2;
size_t idxNextMatch = 0;
while (usedMatchSequence.size() != requiredMatchCount)
{
// find the next match that has not already been used
// and that contains only "unused" player pairs
while (idxNextMatch < remain.size())
{
if (isMatchUsed[idxNextMatch])
{
++idxNextMatch;
continue;
}
break;
}
// if we found a match, store it andint flag
// all other matches with these player pairs as "used"
if (idxNextMatch < remain.size())
{
usedMatchSequence.push_back(idxNextMatch);
std::tuple<int, int> m = remain[idxNextMatch];
// flag all matches with these two pairs
// as "used".
flagMatchesWithPlayerPairOccurence(remain, isMatchUsed, m, true);
// start all over again
idxNextMatch = 0;
}
// if we have an odd number of players and we just
// found a complete match combination, we need to
// make sure that the implicitly selected "bye" player
// is valid. Each player should only have ONE bye
if ((usedMatchSequence.size() == requiredMatchCount) && ((ranking.size() % 2) != 0))
{
std::vector<std::tuple<int, int>> matchSubset;
for (int idx : usedMatchSequence)
{
matchSubset.push_back(remain[idx]);
}
int byePairId = findByePlayerInMatchSet(matchSubset);
if (byePairId >= 0)
{
std::vector<int> potentialBye = getPotentialByePairs(nextMatches);
auto it = find(potentialBye.begin(), potentialBye.end(), byePairId);
// if the selected bye pair is not in the list
// of permitted bye players, we fake a "match not found"
// which causes the deletion of the last match in the
// following code block.
//
// This deletion, in turn, will cause another search iteration
if (it == potentialBye.end())
{
idxNextMatch = remain.size();
}
}
}
// if we couldn't find a match, then the previous match
// selection was wrong. We undo the previous match selection
// and continue with the next index
if (idxNextMatch == remain.size())
{
idxNextMatch = usedMatchSequence.back();
usedMatchSequence.pop_back();
std::tuple<int, int> m = remain[idxNextMatch];
// flag all matches with these two pairs
// as "unused".
flagMatchesWithPlayerPairOccurence(remain, isMatchUsed, m, false);
// continue with the next match
++idxNextMatch;
// stop criterion: if the list of used matches is empty
// and we are requiredMatchCount matches away from the
// end of the match list, there is no solution
if (usedMatchSequence.empty() && (idxNextMatch == (remain.size() - requiredMatchCount + 1)))
{
return false;
}
}
}
return true;
}
//----------------------------------------------------------------------------
void SwissLadderGenerator::flagMatchesWithPlayerPairOccurence(const std::vector<std::tuple<int, int> >& matchSet, std::vector<bool>& flagList,
const std::tuple<int, int>& refMatch, bool newState) const
{
int pp1Id = get<0>(refMatch);
int pp2Id = get<1>(refMatch);
for (size_t i=0; i < matchSet.size(); ++i)
{
// we don't need to check matches that already
// are in the new state
if (flagList[i] == newState) continue;
const std::tuple<int, int>& m = matchSet[i];
int other1Id = get<0>(m);
int other2Id = get<1>(m);
if ((other1Id == pp1Id) || (other1Id == pp2Id) || (other2Id == pp1Id) || (other2Id == pp2Id))
{
flagList[i] = newState;
}
}
}
//----------------------------------------------------------------------------
std::vector<int> SwissLadderGenerator::getPotentialByePairs(const std::vector<std::tuple<int, int> >& optionalAdditionalMatches) const
{
unordered_map<int, int> matchCountCopy = matchCount;
for (const std::tuple<int, int>& m : optionalAdditionalMatches)
{
int pp1Id = get<0>(m);
int pp2Id = get<1>(m);
int& ref1 = matchCountCopy[pp1Id];
++ref1;
int& ref2 = matchCountCopy[pp2Id];
++ref2;
}
int nRounds = optionalAdditionalMatches.empty() ? roundsPlayed : (roundsPlayed + 1);
std::vector<int> result;
for (int ppId : ranking)
{
if (matchCountCopy.at(ppId) == nRounds) result.push_back(ppId);
}
return result;
}
//----------------------------------------------------------------------------
int SwissLadderGenerator::findByePlayerInMatchSet(const std::vector<std::tuple<int, int> >& matchSet) const
{
std::vector<int> allPlayers = ranking;
for (const std::tuple<int, int>& m : matchSet)
{
int ppId = get<0>(m);
auto it = find(allPlayers.begin(), allPlayers.end(), ppId);
// the following "if" should always be true, but let's be conservative...
if (it != allPlayers.end()) allPlayers.erase(it);
ppId = get<1>(m);
it = find(allPlayers.begin(), allPlayers.end(), ppId);
if (it != allPlayers.end()) allPlayers.erase(it);
}
if (allPlayers.empty()) return -1;
return allPlayers[0];
}
//----------------------------------------------------------------------------
}