1 | // License: GPL. For details, see LICENSE file.
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2 | package org.openstreetmap.josm.data.osm;
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3 |
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4 | import java.util.ArrayList;
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5 | import java.util.Collection;
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6 | import java.util.Collections;
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7 | import java.util.LinkedHashMap;
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8 | import java.util.LinkedHashSet;
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9 | import java.util.LinkedList;
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10 | import java.util.List;
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11 | import java.util.Map;
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12 | import java.util.Optional;
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13 | import java.util.Set;
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14 | import java.util.Stack;
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15 |
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16 | import org.openstreetmap.josm.tools.Pair;
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17 |
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18 | /**
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19 | * A directed or undirected graph of nodes.
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20 | * @since 12463 (extracted from CombineWayAction)
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21 | */
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22 | public class NodeGraph {
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23 |
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24 | /**
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25 | * Builds a list of pair of nodes from the given way.
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26 | * @param way way
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27 | * @param directed if {@code true} each pair of nodes will occur once, in the way nodes order.
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28 | * if {@code false} each pair of nodes will occur twice (the pair and its inversed copy)
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29 | * @return a list of pair of nodes from the given way
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30 | */
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31 | public static List<NodePair> buildNodePairs(Way way, boolean directed) {
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32 | List<NodePair> pairs = new ArrayList<>();
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33 | for (Pair<Node, Node> pair: way.getNodePairs(false /* don't sort */)) {
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34 | pairs.add(new NodePair(pair));
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35 | if (!directed) {
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36 | pairs.add(new NodePair(pair).swap());
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37 | }
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38 | }
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39 | return pairs;
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40 | }
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41 |
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42 | /**
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43 | * Builds a list of pair of nodes from the given ways.
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44 | * @param ways ways
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45 | * @param directed if {@code true} each pair of nodes will occur once, in the way nodes order.
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46 | * if {@code false} each pair of nodes will occur twice (the pair and its inversed copy)
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47 | * @return a list of pair of nodes from the given ways
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48 | */
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49 | public static List<NodePair> buildNodePairs(List<Way> ways, boolean directed) {
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50 | List<NodePair> pairs = new ArrayList<>();
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51 | for (Way w: ways) {
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52 | pairs.addAll(buildNodePairs(w, directed));
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53 | }
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54 | return pairs;
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55 | }
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56 |
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57 | /**
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58 | * Builds a new list of pair nodes without the duplicated pairs (including inversed copies).
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59 | * @param pairs existing list of pairs
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60 | * @return a new list of pair nodes without the duplicated pairs
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61 | */
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62 | public static List<NodePair> eliminateDuplicateNodePairs(List<NodePair> pairs) {
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63 | List<NodePair> cleaned = new ArrayList<>();
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64 | for (NodePair p: pairs) {
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65 | if (!cleaned.contains(p) && !cleaned.contains(p.swap())) {
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66 | cleaned.add(p);
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67 | }
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68 | }
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69 | return cleaned;
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70 | }
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71 |
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72 | public static NodeGraph createDirectedGraphFromNodePairs(List<NodePair> pairs) {
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73 | NodeGraph graph = new NodeGraph();
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74 | for (NodePair pair: pairs) {
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75 | graph.add(pair);
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76 | }
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77 | return graph;
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78 | }
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79 |
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80 | public static NodeGraph createDirectedGraphFromWays(Collection<Way> ways) {
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81 | NodeGraph graph = new NodeGraph();
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82 | for (Way w: ways) {
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83 | graph.add(buildNodePairs(w, true /* directed */));
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84 | }
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85 | return graph;
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86 | }
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87 |
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88 | /**
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89 | * Create an undirected graph from the given node pairs.
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90 | * @param pairs Node pairs to build the graph from
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91 | * @return node graph structure
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92 | */
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93 | public static NodeGraph createUndirectedGraphFromNodeList(List<NodePair> pairs) {
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94 | NodeGraph graph = new NodeGraph();
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95 | for (NodePair pair: pairs) {
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96 | graph.add(pair);
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97 | graph.add(pair.swap());
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98 | }
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99 | return graph;
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100 | }
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101 |
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102 | /**
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103 | * Create an undirected graph from the given ways, but prevent reversing of all
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104 | * non-new ways by fix one direction.
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105 | * @param ways Ways to build the graph from
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106 | * @return node graph structure
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107 | * @since 8181
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108 | */
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109 | public static NodeGraph createUndirectedGraphFromNodeWays(Collection<Way> ways) {
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110 | NodeGraph graph = new NodeGraph();
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111 | for (Way w: ways) {
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112 | graph.add(buildNodePairs(w, false /* undirected */));
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113 | }
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114 | return graph;
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115 | }
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116 |
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117 | public static NodeGraph createNearlyUndirectedGraphFromNodeWays(Collection<Way> ways) {
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118 | boolean dir = true;
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119 | NodeGraph graph = new NodeGraph();
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120 | for (Way w: ways) {
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121 | if (!w.isNew()) {
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122 | /* let the first non-new way give the direction (see #5880) */
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123 | graph.add(buildNodePairs(w, dir));
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124 | dir = false;
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125 | } else {
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126 | graph.add(buildNodePairs(w, false /* undirected */));
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127 | }
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128 | }
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129 | return graph;
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130 | }
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131 |
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132 | private final Set<NodePair> edges;
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133 | private int numUndirectedEges;
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134 | private final Map<Node, List<NodePair>> successors = new LinkedHashMap<>();
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135 | private final Map<Node, List<NodePair>> predecessors = new LinkedHashMap<>();
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136 |
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137 | protected void rememberSuccessor(NodePair pair) {
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138 | if (successors.containsKey(pair.getA())) {
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139 | if (!successors.get(pair.getA()).contains(pair)) {
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140 | successors.get(pair.getA()).add(pair);
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141 | }
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142 | } else {
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143 | List<NodePair> l = new ArrayList<>();
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144 | l.add(pair);
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145 | successors.put(pair.getA(), l);
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146 | }
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147 | }
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148 |
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149 | protected void rememberPredecessors(NodePair pair) {
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150 | if (predecessors.containsKey(pair.getB())) {
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151 | if (!predecessors.get(pair.getB()).contains(pair)) {
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152 | predecessors.get(pair.getB()).add(pair);
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153 | }
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154 | } else {
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155 | List<NodePair> l = new ArrayList<>();
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156 | l.add(pair);
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157 | predecessors.put(pair.getB(), l);
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158 | }
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159 | }
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160 |
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161 | protected boolean isTerminalNode(Node n) {
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162 | if (successors.get(n) == null) return false;
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163 | if (successors.get(n).size() != 1) return false;
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164 | if (predecessors.get(n) == null) return true;
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165 | if (predecessors.get(n).size() == 1) {
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166 | NodePair p1 = successors.get(n).get(0);
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167 | NodePair p2 = predecessors.get(n).get(0);
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168 | return p1.equals(p2.swap());
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169 | }
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170 | return false;
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171 | }
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172 |
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173 | protected void prepare() {
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174 | Set<NodePair> undirectedEdges = new LinkedHashSet<>();
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175 | successors.clear();
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176 | predecessors.clear();
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177 |
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178 | for (NodePair pair: edges) {
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179 | if (!undirectedEdges.contains(pair) && !undirectedEdges.contains(pair.swap())) {
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180 | undirectedEdges.add(pair);
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181 | }
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182 | rememberSuccessor(pair);
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183 | rememberPredecessors(pair);
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184 | }
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185 | numUndirectedEges = undirectedEdges.size();
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186 | }
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187 |
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188 | /**
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189 | * Constructs a new {@code NodeGraph}.
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190 | */
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191 | public NodeGraph() {
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192 | edges = new LinkedHashSet<>();
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193 | }
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194 |
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195 | /**
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196 | * Add a node pair.
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197 | * @param pair node pair
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198 | */
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199 | public void add(NodePair pair) {
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200 | if (!edges.contains(pair)) {
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201 | edges.add(pair);
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202 | }
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203 | }
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204 |
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205 | /**
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206 | * Add a list of node pairs.
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207 | * @param pairs list of node pairs
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208 | */
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209 | public void add(Collection<NodePair> pairs) {
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210 | for (NodePair pair: pairs) {
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211 | add(pair);
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212 | }
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213 | }
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214 |
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215 | protected Set<Node> getTerminalNodes() {
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216 | Set<Node> ret = new LinkedHashSet<>();
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217 | for (Node n: getNodes()) {
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218 | if (isTerminalNode(n)) {
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219 | ret.add(n);
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220 | }
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221 | }
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222 | return ret;
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223 | }
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224 |
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225 | protected List<NodePair> getOutboundPairs(NodePair pair) {
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226 | return getOutboundPairs(pair.getB());
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227 | }
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228 |
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229 | protected List<NodePair> getOutboundPairs(Node node) {
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230 | return Optional.ofNullable(successors.get(node)).orElseGet(Collections::emptyList);
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231 | }
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232 |
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233 | protected Set<Node> getNodes() {
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234 | Set<Node> nodes = new LinkedHashSet<>(2 * edges.size());
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235 | for (NodePair pair: edges) {
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236 | nodes.add(pair.getA());
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237 | nodes.add(pair.getB());
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238 | }
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239 | return nodes;
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240 | }
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241 |
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242 | protected boolean isSpanningWay(Stack<NodePair> way) {
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243 | return numUndirectedEges == way.size();
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244 | }
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245 |
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246 | protected List<Node> buildPathFromNodePairs(Stack<NodePair> path) {
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247 | List<Node> ret = new LinkedList<>();
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248 | for (NodePair pair: path) {
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249 | ret.add(pair.getA());
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250 | }
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251 | ret.add(path.peek().getB());
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252 | return ret;
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253 | }
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254 |
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255 | /**
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256 | * Tries to find a spanning path starting from node <code>startNode</code>.
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257 | *
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258 | * Traverses the path in depth-first order.
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259 | *
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260 | * @param startNode the start node
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261 | * @return the spanning path; null, if no path is found
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262 | */
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263 | protected List<Node> buildSpanningPath(Node startNode) {
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264 | if (startNode != null) {
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265 | Stack<NodePair> path = new Stack<>();
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266 | Stack<NodePair> nextPairs = new Stack<>();
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267 | nextPairs.addAll(getOutboundPairs(startNode));
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268 | while (!nextPairs.isEmpty()) {
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269 | NodePair cur = nextPairs.pop();
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270 | if (!path.contains(cur) && !path.contains(cur.swap())) {
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271 | while (!path.isEmpty() && !path.peek().isPredecessorOf(cur)) {
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272 | path.pop();
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273 | }
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274 | path.push(cur);
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275 | if (isSpanningWay(path)) return buildPathFromNodePairs(path);
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276 | nextPairs.addAll(getOutboundPairs(path.peek()));
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277 | }
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278 | }
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279 | }
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280 | return Collections.emptyList();
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281 | }
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282 |
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283 | /**
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284 | * Tries to find a path through the graph which visits each edge (i.e.
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285 | * the segment of a way) exactly once.
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286 | *
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287 | * @return the path; null, if no path was found
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288 | */
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289 | public List<Node> buildSpanningPath() {
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290 | prepare();
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291 | // try to find a path from each "terminal node", i.e. from a
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292 | // node which is connected by exactly one undirected edges (or
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293 | // two directed edges in opposite direction) to the graph. A
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294 | // graph built up from way segments is likely to include such
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295 | // nodes, unless all ways are closed.
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296 | // In the worst case this loops over all nodes which is very slow for large ways.
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297 | //
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298 | Set<Node> nodes = getTerminalNodes();
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299 | nodes = nodes.isEmpty() ? getNodes() : nodes;
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300 | for (Node n: nodes) {
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301 | List<Node> path = buildSpanningPath(n);
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302 | if (!path.isEmpty())
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303 | return path;
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304 | }
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305 | return null;
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306 | }
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307 | }
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