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
/* 2014
 * Maciej Szeptuch
 * II UWr
 */
#include "kollib.h"
#include "message.h"

#define NDEBUG

#include <cassert>
#include <cstdio>
#include <algorithm>
#include <random>
#include <functional>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <chrono>

using namespace std;

typedef long long               ll;
typedef unsigned long long      llu;
typedef vector<ll>              Array;
typedef vector<pair<ll, ll>>    Graph;
typedef unordered_map<ll, ll>   Map;

ll  node,
    nodes,
    students,
    queries;
llu workers;


// SERVER
Graph graph[512];
Array mapping;

void    runServer(void);
void    chooseStartPoints(void);
void    renumber(void);
ll      renumber(ll vert);
void    readGraph(void);
void    solve(void);


// WORKER
Array stop;
Array edge;

void    runWorker(void);
void    readQueries(void);
ll      readStartPoints(void);
void    traverse(ll start);
void    sendVertex(ll &last, ll &current, ll &count);


int main(void)
{
    node    = MyNodeId();
    nodes   = NumberOfNodes();
    workers = nodes - 1;

    students    = NumberOfStudents();
    queries     = NumberOfQueries();

    nodes   = min(nodes, students + 1);

    // Too many workers
    if(node >= nodes)
        return 0;

    if(!node)
        runServer();

    else
        runWorker();

    return 0;
}

/******************************************************************************
 * SERVER
 *****************************************************************************/
inline
void runServer(void)
{
#ifndef NDEBUG
    assert(workers > 0 && "Invalid number of workers");
    fprintf(stderr, "Running server\n");
    fprintf(stderr, "    Nodes:     %llu\n", nodes);
    fprintf(stderr, "    Students:  %llu\n", students);
    fprintf(stderr, "    Queries:   %llu\n", queries);
    fprintf(stderr, "    Workers:   %llu\n", workers);
#endif // NDEBUG

    // Choose worker start points
    chooseStartPoints();

    // Renumber vertices
    renumber();

    // Read graph edges
    readGraph();

    // Calculate answer
    solve();
}

inline
void chooseStartPoints(void)
{
    default_random_engine           rand;
    random_device                   device;
    uniform_int_distribution<ll>    distribution(1, students);
    auto random = bind(distribution, rand);
    set<ll> startPoints;

#ifndef NDEBUG
    fprintf(stderr, "Choosing start points\n");
#endif // NDEBUG

    rand.seed(device());
    while(startPoints.size() < workers)
        startPoints.insert(random());

    mapping = Array(begin(startPoints), end(startPoints));
#ifndef NDEBUG
    for(auto p = 0LLU; p < workers; ++ p)
        fprintf(stderr, "Worker %llu got %llu as starting point\n", p + 1, mapping[p]);

#endif // NDEBUG

    for(auto w = 0LLU; w < workers; ++ w)
    {
        for(auto p = 0LLU; p < workers; ++ p)
            PutLL(w + 1, mapping[p]);

        Send(w + 1);
#ifndef NDEBUG
        fprintf(stderr, "Sent start points to %llu\n", w + 1);
#endif // NDEBUG
    }
}

inline
void renumber(void)
{
#ifndef NDEBUG
    fprintf(stderr, "Renumbering vertices\n");
#endif // NDEBUG
    for(auto q = 0LL; q < queries; ++ q)
    {
        mapping.push_back(QueryFrom(q + 1));
        mapping.push_back(QueryTo(q + 1));
    }

    sort(begin(mapping), end(mapping));
    mapping.erase(unique(begin(mapping), end(mapping)), end(mapping));
#ifndef NDEBUG
    assert(mapping.size() < 512 && "Invalid mapping size");
    fprintf(stderr, "Renumbered %lu vertices\n", mapping.size());
#endif // NDEBUG
}

inline
ll renumber(ll vert)
{
#ifndef NDEBUG
    assert(binary_search(begin(mapping), end(mapping), vert) && "Not mapped vertex?");
#endif // NDEBUG
    return distance(begin(mapping), lower_bound(begin(mapping), end(mapping), vert));
}

inline
void readGraph(void)
{
#ifndef NDEBUG
    fprintf(stderr, "Reading graph edges\n");
#endif // NDEBUG

    unordered_set<ll> finished;
    for(auto w = 0LLU; w < workers; ++ w)
        finished.insert(w);

    while(!finished.empty())
    {
        ll sender = Receive(-1);
#ifndef NDEBUG
        assert(sender > 0 && "Error receiving graph edges");
#endif // NDEBUG

        ll action = GetLL(sender);

        // Worker has finished processing its part
        if(action == -1)
        {
            auto repr = finished.find(sender - 1);
#ifndef NDEBUG
            assert(repr != end(finished) && "Invalid communication");
            fprintf(stderr, "Received End Of Work from %llu\n", sender);
#endif // NDEBUG
            finished.erase(repr);
            continue;
        }

        ll  from    = action,
            to      = GetLL(sender),
            cost    = GetLL(sender);

#ifndef NDEBUG
        fprintf(stderr, "Received (%lld, %lld, %lld) edge from %llu\n", from, to, cost, sender);
#endif // NDEBUG

        from    = renumber(from);
        to      = renumber(to);

        graph[from].push_back(make_pair(to, cost));
    }
}

inline
void solve(void)
{
#ifndef NDEBUG
    fprintf(stderr, "Calculating shortest paths\n");
#endif // NDEBUG

    ll distance[512];
    fill(distance, distance + 512, (1LL << 31));

    distance[0] = 0;

    ll current = 0;
#ifndef NDEBUG
    llu cnt = 0;
#endif // NDEBUG

    while(true)
    {
#ifndef NDEBUG
        assert(graph[current].size() == 2 && "Incomplete graph");
        ++ cnt;
#endif // NDEBUG

        ll g = distance[graph[current][0].first] < (1LL << 31);
        if(distance[graph[current][g].first] < (1LL << 31))
            break;

        auto &next = graph[current][g];
        distance[next.first] = min(distance[next.first], distance[current] + next.second);
        current = next.first;
    }

#ifndef NDEBUG
    assert(cnt == mapping.size() && "Incomplete graph");
    fprintf(stderr, "Printing answer\n");
#endif // NDEBUG

    for(auto q = 0; q < queries; ++ q)
    {
        ll dist = abs(distance[renumber(QueryFrom(q + 1))] - distance[renumber(QueryTo(q + 1))]);
        printf("%lld\n", min(dist, students - dist));
    }
}

/******************************************************************************
 * WORKER
 *****************************************************************************/
inline
void runWorker(void)
{
#ifndef NDEBUG
    fprintf(stderr, "Running %llu worker\n", node);
#endif // NDEBUG

    ll start;

    // Read Queries
    readQueries();

    // Read start points
    start = readStartPoints();

    // Traverse cycle + send graph edges
    traverse(start);

    // Finished
    PutLL(0, -1);
    Send(0);
}

inline
void readQueries(void)
{
#ifndef NDEBUG
    fprintf(stderr, "Reading queries\n");
#endif // NDEBUG

    for(auto q = 0; q < queries; ++ q)
    {
        edge.push_back(QueryFrom(q + 1));
        edge.push_back(QueryTo(q + 1));
    }

    sort(begin(edge), end(edge));
    edge.erase(unique(begin(edge), end(edge)), end(edge));
}

inline
ll readStartPoints(void)
{
    ll start = -1;
#ifndef NDEBUG
    fprintf(stderr, "Reading start points\n");
#endif // NDEBUG

    Receive(0);
    for(auto w = 0LL; w < nodes - 1; ++ w)
    {
        ll act = GetLL(0);
        if(w + 1 == node)
            start = act;

        stop.push_back(act);
    }

#ifndef NDEBUG
    assert(is_sorted(begin(stop), end(stop)) && unique(begin(stop), end(stop)) == end(stop) && "Communication error");
    fprintf(stderr, "Worker %llu starting in %lld point\n", node, start);
    assert(start > 0 && "Invalid start point");
#endif // NDEBUG

    return start;
}

inline
void traverse(ll start)
{
    ll previous = start,
       last     = start,
       current  = start,
       count    = 0;

    // Walking "left"
    do
    {
        ll next = FirstNeighbor(current);
        if(next == previous)
            next = SecondNeighbor(current);

        previous    = current;
        current     = next;
        ++ count;
        if(binary_search(begin(edge), end(edge), current))
            sendVertex(last, current, count);
    }
    while(!binary_search(begin(stop), end(stop), current));

    if(last != current)
        sendVertex(last, current, count);

#ifndef NDEBUG
    fprintf(stderr, "'left' went from %lld to %lld\n", start, current);
#endif // NDEBUG

    previous    = start;
    last        = start;
    current     = start;
    count       = 0;
    // Walking "right"
    do
    {
        ll next = SecondNeighbor(current);
        if(next == previous)
            next = FirstNeighbor(current);

        previous    = current;
        current     = next;
        ++ count;
        if(binary_search(begin(edge), end(edge), current))
            sendVertex(last, current, count);
    }
    while(!binary_search(begin(stop), end(stop), current));

    if(last != current)
        sendVertex(last, current, count);

#ifndef NDEBUG
    fprintf(stderr, "'right' went from %lld to %lld\n", start, current);
#endif // NDEBUG
}

inline
void sendVertex(ll &last, ll &current, ll &count)
{
#ifndef NDEBUG
    fprintf(stderr, "Sending (%lld, %lld, %lld)\n", last, current, count);
#endif // NDEBUG
    PutLL(0, last);
    PutLL(0, current);
    PutLL(0, count);
    Send(0);
    last = current;
    count = 0;
}