#include <algorithm> #include <cstdio> #include <utility> #include <vector> #include "message.h" #include "sabotaz.h" // Information about nodes: // ------------------------ struct { int number_of_nodes; int my_id; void Init() { number_of_nodes = NumberOfNodes(); my_id = MyNodeId(); } } NodeInfo; // My queue: // --------- struct { int values[200005]; // It should be large enough to store 2 * MAX_NODES. int b, e; void Init() { b = e = 0; } void Add(int x) { values[e++] = x; } int Pop() { return values[b++]; } int Size() { return e - b; } } Queue; // This node's tasks: // ------------------ struct { // 1. Range of edges this node processes. int edge_min, edge_max; // 2. Sequence of nodes with whom this node merges its results. std::vector<int> merges_with; // 3. If this node is the last one, sends_to_whom = -1; // otherwise sends_to_whom contains id of the node which will merge // this node's results with its results. int sends_to_whom; void Init() { const int n = NumberOfIsles(); const int m = NumberOfBridges(); const int edge_range_width = (m + NodeInfo.number_of_nodes - 1) / NodeInfo.number_of_nodes; edge_min = std::min(NodeInfo.my_id * edge_range_width, m); edge_max = std::min((NodeInfo.my_id + 1) * edge_range_width - 1, m - 1); Queue.Init(); for (int i = 0; i < NodeInfo.number_of_nodes; i++) { Queue.Add(i); } sends_to_whom = -1; while (Queue.Size() >= 2) { const int node_a = Queue.Pop(); const int node_b = Queue.Pop(); if (node_a == NodeInfo.my_id) { merges_with.push_back(node_b); } if (node_b == NodeInfo.my_id) { sends_to_whom = node_a; } Queue.Add(node_a); } } } Tasks; // Find & Union: // ------------- struct { int link[200005]; std::vector<int> group[200005]; void Init(int n) { for (int i = 1; i <= n; i++) { link[i] = i; } } int Find(int w) { if (link[w] == w) { return w; } return link[w] = Find(link[w]); } void Union(int u, int v) { link[Find(u)] = Find(v); } void MakeGroups(int n) { for (int i = 1; i <= n; i++) { group[i].clear(); } for (int i = 1; i <= n; i++) { group[Find(i)].push_back(i); } } const std::vector<int>& GetGroup(int w) { return group[w]; } } FindUnion; // Graph and operations on the graph: // ---------------------------------- struct { int n; // Number of vertices and edges in the whole graph. // The graph has only a subset of edges from the original graph. std::vector<int> graph[200005]; int pre_counter; // Counter for the pre_order numbers. int pre_order[200005]; int low[200005]; int number_of_bridges; void Init() { n = NumberOfIsles(); for (int i = Tasks.edge_min; i <= Tasks.edge_max; i++) { const int edge_a = BridgeEndA(i) + 1; // Here nodes are numbered const int edge_b = BridgeEndB(i) + 1; // from 1 to n (hence +1). graph[edge_a].push_back(edge_b); graph[edge_b].push_back(edge_a); } } void DfsForLow(int w, int father) { pre_order[w] = pre_counter++; low[w] = pre_order[w]; for (int neighbour : graph[w]) { if (neighbour == father) { // Prevents from going back to father using the same edge, // but blocks only one such edge. father = -1; continue; } if (pre_order[neighbour]) { // This neighbour has been already visited. low[w] = std::min(low[w], pre_order[neighbour]); } else { DfsForLow(neighbour, w); low[w] = std::min(low[w], low[neighbour]); } } } bool IsABridge(int a, int b) { if (pre_order[a] > pre_order[b]) { std::swap(a, b); } // Now a is above b. return low[b] > pre_order[a]; } void ComputeLow() { for (int i = 1; i <= n; i++) { pre_order[i] = 0; } pre_counter = 1; for (int i = 1; i <= n; i++) { if (pre_order[i] == 0) { DfsForLow(i, -1); } } } void Canonize() { number_of_bridges = 0; ComputeLow(); FindUnion.Init(n); for (int w = 1; w <= n; w++) { int graph_size = graph[w].size(); for (int i = 0; i < graph_size; i++) { if (!IsABridge(w, graph[w][i])) { FindUnion.Union(w, graph[w][i]); std::swap(graph[w][i], graph[w][graph_size - 1]); graph_size--; i--; } else { number_of_bridges++; } } graph[w].resize(graph_size); } number_of_bridges /= 2; // Each bridge was counted two times. FindUnion.MakeGroups(n); for (int w = 1; w <= n; w++) { const std::vector<int>& group = FindUnion.GetGroup(w); if ((int) group.size() > 1) { for (int i = 1; i < group.size(); i++) { graph[group[i - 1]].push_back(group[i]); graph[group[i]].push_back(group[i - 1]); } graph[group[0]].push_back(group.back()); graph[group.back()].push_back(group[0]); } } } void MergeWith(int with_whom) { Receive(with_whom); int number_of_edges = GetInt(with_whom); while (number_of_edges--) { const int edge_a = GetInt(with_whom); const int edge_b = GetInt(with_whom); graph[edge_a].push_back(edge_b); graph[edge_b].push_back(edge_a); } } void SendTo(int to_whom) { std::vector<std::pair<int, int>> edges; for (int w = 1; w <= n; w++) { for (int neighbour : graph[w]) { if (neighbour < w) { edges.emplace_back(neighbour, w); } } } PutInt(to_whom, (int) edges.size()); for (const auto& edge : edges) { PutInt(to_whom, edge.first); PutInt(to_whom, edge.second); } Send(to_whom); } } Graph; int main() { NodeInfo.Init(); Tasks.Init(); Graph.Init(); Graph.Canonize(); for (int node_id : Tasks.merges_with) { Graph.MergeWith(node_id); Graph.Canonize(); } if (Tasks.sends_to_whom == -1) { printf("%d\n", Graph.number_of_bridges); } else { Graph.SendTo(Tasks.sends_to_whom); } return 0; }
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 | #include <algorithm> #include <cstdio> #include <utility> #include <vector> #include "message.h" #include "sabotaz.h" // Information about nodes: // ------------------------ struct { int number_of_nodes; int my_id; void Init() { number_of_nodes = NumberOfNodes(); my_id = MyNodeId(); } } NodeInfo; // My queue: // --------- struct { int values[200005]; // It should be large enough to store 2 * MAX_NODES. int b, e; void Init() { b = e = 0; } void Add(int x) { values[e++] = x; } int Pop() { return values[b++]; } int Size() { return e - b; } } Queue; // This node's tasks: // ------------------ struct { // 1. Range of edges this node processes. int edge_min, edge_max; // 2. Sequence of nodes with whom this node merges its results. std::vector<int> merges_with; // 3. If this node is the last one, sends_to_whom = -1; // otherwise sends_to_whom contains id of the node which will merge // this node's results with its results. int sends_to_whom; void Init() { const int n = NumberOfIsles(); const int m = NumberOfBridges(); const int edge_range_width = (m + NodeInfo.number_of_nodes - 1) / NodeInfo.number_of_nodes; edge_min = std::min(NodeInfo.my_id * edge_range_width, m); edge_max = std::min((NodeInfo.my_id + 1) * edge_range_width - 1, m - 1); Queue.Init(); for (int i = 0; i < NodeInfo.number_of_nodes; i++) { Queue.Add(i); } sends_to_whom = -1; while (Queue.Size() >= 2) { const int node_a = Queue.Pop(); const int node_b = Queue.Pop(); if (node_a == NodeInfo.my_id) { merges_with.push_back(node_b); } if (node_b == NodeInfo.my_id) { sends_to_whom = node_a; } Queue.Add(node_a); } } } Tasks; // Find & Union: // ------------- struct { int link[200005]; std::vector<int> group[200005]; void Init(int n) { for (int i = 1; i <= n; i++) { link[i] = i; } } int Find(int w) { if (link[w] == w) { return w; } return link[w] = Find(link[w]); } void Union(int u, int v) { link[Find(u)] = Find(v); } void MakeGroups(int n) { for (int i = 1; i <= n; i++) { group[i].clear(); } for (int i = 1; i <= n; i++) { group[Find(i)].push_back(i); } } const std::vector<int>& GetGroup(int w) { return group[w]; } } FindUnion; // Graph and operations on the graph: // ---------------------------------- struct { int n; // Number of vertices and edges in the whole graph. // The graph has only a subset of edges from the original graph. std::vector<int> graph[200005]; int pre_counter; // Counter for the pre_order numbers. int pre_order[200005]; int low[200005]; int number_of_bridges; void Init() { n = NumberOfIsles(); for (int i = Tasks.edge_min; i <= Tasks.edge_max; i++) { const int edge_a = BridgeEndA(i) + 1; // Here nodes are numbered const int edge_b = BridgeEndB(i) + 1; // from 1 to n (hence +1). graph[edge_a].push_back(edge_b); graph[edge_b].push_back(edge_a); } } void DfsForLow(int w, int father) { pre_order[w] = pre_counter++; low[w] = pre_order[w]; for (int neighbour : graph[w]) { if (neighbour == father) { // Prevents from going back to father using the same edge, // but blocks only one such edge. father = -1; continue; } if (pre_order[neighbour]) { // This neighbour has been already visited. low[w] = std::min(low[w], pre_order[neighbour]); } else { DfsForLow(neighbour, w); low[w] = std::min(low[w], low[neighbour]); } } } bool IsABridge(int a, int b) { if (pre_order[a] > pre_order[b]) { std::swap(a, b); } // Now a is above b. return low[b] > pre_order[a]; } void ComputeLow() { for (int i = 1; i <= n; i++) { pre_order[i] = 0; } pre_counter = 1; for (int i = 1; i <= n; i++) { if (pre_order[i] == 0) { DfsForLow(i, -1); } } } void Canonize() { number_of_bridges = 0; ComputeLow(); FindUnion.Init(n); for (int w = 1; w <= n; w++) { int graph_size = graph[w].size(); for (int i = 0; i < graph_size; i++) { if (!IsABridge(w, graph[w][i])) { FindUnion.Union(w, graph[w][i]); std::swap(graph[w][i], graph[w][graph_size - 1]); graph_size--; i--; } else { number_of_bridges++; } } graph[w].resize(graph_size); } number_of_bridges /= 2; // Each bridge was counted two times. FindUnion.MakeGroups(n); for (int w = 1; w <= n; w++) { const std::vector<int>& group = FindUnion.GetGroup(w); if ((int) group.size() > 1) { for (int i = 1; i < group.size(); i++) { graph[group[i - 1]].push_back(group[i]); graph[group[i]].push_back(group[i - 1]); } graph[group[0]].push_back(group.back()); graph[group.back()].push_back(group[0]); } } } void MergeWith(int with_whom) { Receive(with_whom); int number_of_edges = GetInt(with_whom); while (number_of_edges--) { const int edge_a = GetInt(with_whom); const int edge_b = GetInt(with_whom); graph[edge_a].push_back(edge_b); graph[edge_b].push_back(edge_a); } } void SendTo(int to_whom) { std::vector<std::pair<int, int>> edges; for (int w = 1; w <= n; w++) { for (int neighbour : graph[w]) { if (neighbour < w) { edges.emplace_back(neighbour, w); } } } PutInt(to_whom, (int) edges.size()); for (const auto& edge : edges) { PutInt(to_whom, edge.first); PutInt(to_whom, edge.second); } Send(to_whom); } } Graph; int main() { NodeInfo.Init(); Tasks.Init(); Graph.Init(); Graph.Canonize(); for (int node_id : Tasks.merges_with) { Graph.MergeWith(node_id); Graph.Canonize(); } if (Tasks.sends_to_whom == -1) { printf("%d\n", Graph.number_of_bridges); } else { Graph.SendTo(Tasks.sends_to_whom); } return 0; } |