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
#include <message.h>
#include "kollib.h"
#include <unordered_set>
#include <climits>
#include <cstdio>
#include <utility>
#include <map>

typedef std::unordered_set<int> S;
typedef std::pair<int, int> P;
struct Res
{
	Res() {}
	Res(int to, int toCnt) :
		_to1(to), _to1Cnt(toCnt),
		_to2(-1), _to2Cnt(0)
	{} 

	void add(int to, int toCnt)
	{
		_to2 = to;
		_to2Cnt = toCnt;
	}
	void setCutoffRes(int to, int cnt)
	{
		if (INT_MAX == _to1)
		{
			_to1 = to;
			_to1Cnt = cnt;
		}
		else
		{
			_to2 = to;
			_to2Cnt = cnt;
		}
	}
	int _to1;
	int _to1Cnt;
	int _to2;
	int _to2Cnt;
};
typedef std::map<int, Res> M;

void sendOrder(int who, int startNode, int neighbour)
{
	PutInt(who, startNode);
	PutInt(who, neighbour);
	Send(who);
}

int receiveResult(M &m, int &cutoff)
{
	int node = Receive(-1);
	int val = GetInt(node);
	if (val != -1)
	{
		int from = GetInt(node);
		// get real message with result
		int count = GetInt(node);
		auto found = m.find(from);
		if (found == m.end())
		{
			m[from] = Res(val, count);
		}
		else
		{
			found->second.add(val, count);
		}
		if (INT_MAX == val) cutoff = from;
	}
	return node;
}

const int MAXSEARCH = 500000000;

P getImportant( const S &s, int start, int neighbour )
{
	int result = 1;

	while (s.find(neighbour) == s.end() && result <= MAXSEARCH)
	{
		int fn = FirstNeighbor(neighbour);
		if (fn != start)
		{
			start = neighbour;
			neighbour = fn;
			++result;
		}
		else if ((fn = SecondNeighbor(neighbour)) != start)
		{
			start = neighbour;
			neighbour = fn;
			++result;
		}
	}

	return P(result <= MAXSEARCH ? neighbour : INT_MAX, result);
}

void output(const M &m, int from, int to)
{
	int count = 0;
	int prev = from;
	while (from != to)
	{
		auto f = m.find(from);
		if (f->second._to1 != prev)
		{
			prev = from;
			count += f->second._to1Cnt;
			from = f->second._to1;
		}
		else
		{
			prev = from;
			count += f->second._to2Cnt;
			from = f->second._to2;
		}
	}
	printf("%d\n", std::min(count, NumberOfStudents()-count));
}

void countCutoff(M &m, int cutoff)
{
	Res &start = m[cutoff];
	int prev = cutoff;

	int next = 0;
	int count = 0;
	if (start._to1 != INT_MAX)
	{
		next = start._to1;
		count = start._to1Cnt;
	}
	else
	{
		next = start._to2;
		count = start._to2Cnt;
	}
	bool finish = false;
	do
	{
		auto f = m.find(next);
		if (f->second._to1 == INT_MAX || f->second._to2 == INT_MAX)
		{
			f->second.setCutoffRes(cutoff, NumberOfStudents()-count);
			start.setCutoffRes(next, NumberOfStudents()-count);
			finish = true;
		}
		else
		{
			if (f->second._to1 != prev)
			{
				prev = next;
				count += f->second._to1Cnt;
				next = f->second._to1;
			}
			else
			{
				prev = next;
				count += f->second._to2Cnt;
				next = f->second._to2;
			}
		}
	}
	while (!finish);
}

int main()
{
	S s;
	int qnum = NumberOfQueries();
	s.reserve(2*qnum);

	for (int i = 0; i < qnum; ++i)
	{
		s.insert(QueryFrom(i+1));
		s.insert(QueryTo(i+1));
	}

	if (MyNodeId() == 0)
	{
		M m;
		int numnodes = NumberOfNodes();
		int cutoff = -1;
		for (auto it = s.cbegin(); it != s.cend(); ++it)
		{
			auto node = receiveResult(m, cutoff);
			sendOrder(node, *it, FirstNeighbor(*it));
			node = receiveResult(m, cutoff);
			sendOrder(node, *it, SecondNeighbor(*it));
		}
		for (int i = 1; i < numnodes; ++i)
		{
			auto node = receiveResult(m, cutoff);
			PutInt(node, -1);
			Send(node);
		}
		if (cutoff != -1)
		{
			countCutoff(m, cutoff);
		}
		// now, compute and print results
		for (int i = 0; i < qnum; ++i)
		{
			output(m, QueryFrom(i+1), QueryTo(i+1));
		}
	}
	else
	{
		PutInt(0, -1);
		Send(0);
		bool finish = false;
		do {
			Receive(0);
			int start = GetInt(0);
			if (start != -1)
			{
				int neighbour = GetInt(0);
				// now, find the important neighbour
				P p = getImportant(s, start, neighbour);
				PutInt(0, p.first); // send the answer
				PutInt(0, start);
				PutInt(0, p.second);
				Send(0);
			}
			else finish = true;
		} while (!finish);
	}

	return 0;
}