import java.io.IOException; import java.io.InputStream; import java.util.InputMismatchException; import java.util.Iterator; import java.util.LinkedList; public class kon { private static int highestNodeIndex; public static void main(String... args) { FastScanner scanner = new FastScanner(System.in); highestNodeIndex = scanner.nextInt(); int numberOfLines = scanner.nextInt(); Node[] nodes = new Node[highestNodeIndex + 1]; LinkedList<Node> graph = new LinkedList<>(); for (int index = 1; index <= highestNodeIndex; index++) { Node node = new Node(index); nodes[index] = node; graph.add(node); } for (int i = 0; i < numberOfLines; i++) { Node source = nodes[scanner.nextInt()]; Node target = nodes[scanner.nextInt()]; source.targets.add(target); } LinkedList<Node> cycle = findCycle(graph); if (cycle == null) { System.out.println("NIE"); return; } LinkedList<Integer> hubs = findHubs(cycle, graph); if (hubs.isEmpty()) { printHubs(hubs); return; } for (Integer hub : hubs) { nodes[hub].targets.clear(); } cycle = findCycle(graph); if (cycle == null) { printHubs(hubs); return; } else { printHubs(new LinkedList<Integer>()); } } private static void printHubs(LinkedList<Integer> hubs) { System.out.println(hubs.size()); Iterator<Integer> iterator = hubs.iterator(); if (iterator.hasNext()) { System.out.print(iterator.next()); } while (iterator.hasNext()) { System.out.print(" "); System.out.print(iterator.next()); } System.out.println(); } private static LinkedList<Integer> findHubs(LinkedList<Node> cycle, LinkedList<Node> graph) { boolean[] isInCycle = new boolean[highestNodeIndex + 1]; boolean[] isInPath = new boolean[highestNodeIndex + 1]; int[] isClouded = new int[highestNodeIndex + 1]; boolean[] canBeDetoured = new boolean[highestNodeIndex + 1]; for (Node cycleNode : cycle) { isInCycle[cycleNode.index] = true; } LinkedList<Node> cloudStarters = new LinkedList<>(cycle); int numberOfDetours = 0; boolean[] isDetourEnd = new boolean[highestNodeIndex + 1]; while (!cloudStarters.isEmpty()) { Node cloudStarter = cloudStarters.removeFirst(); if (isDetourEnd[cloudStarter.index]) { isDetourEnd[cloudStarter.index] = false; numberOfDetours--; } if (numberOfDetours > 0) { canBeDetoured[cloudStarter.index] = true; } LinkedList<Node> path = new LinkedList<Node>(); path.add(cloudStarter); isInPath[cloudStarter.index] = true; while (!path.isEmpty()) { Node tail = path.getLast(); if (!tail.targets.isEmpty()) { Node target = tail.targets.removeLast(); if (isInCycle[target.index]) { if (!isDetourEnd[target.index]) { isDetourEnd[target.index] = true; numberOfDetours++; } isClouded[tail.index] = target.index; } else if (isInPath[target.index]) { // another cycle!!! return new LinkedList<Integer>(); } else if (isClouded[target.index] != 0) { int cloudedBy = isClouded[target.index]; isClouded[tail.index] = cloudedBy; if (!isDetourEnd[cloudedBy]) { isDetourEnd[cloudedBy] = true; numberOfDetours++; } } else { isInPath[target.index] = true; path.add(target); } } else { isInPath[tail.index] = false; path.removeLast(); } } } for (Node cycleNode : cycle) { if (numberOfDetours > 0) { if (isDetourEnd[cycleNode.index]) { isDetourEnd[cycleNode.index] = false; numberOfDetours--; } } if (numberOfDetours > 0) { canBeDetoured[cycleNode.index] = true; } else { break; } } LinkedList<Integer> hubs = new LinkedList<>(); for (int i = 1; i <= highestNodeIndex; i++) { if (isInCycle[i] && !canBeDetoured[i]) { hubs.add(i); } } return hubs; } private static LinkedList<Node> findCycle(LinkedList<Node> graph) { LinkedList<Node> startCandidates = new LinkedList<>(graph); while (!startCandidates.isEmpty()) { LinkedList<Node> cycle = new LinkedList<>(); boolean[] isInCycle = new boolean[highestNodeIndex + 1]; cycle.add(startCandidates.removeFirst()); isInCycle[cycle.getFirst().index] = true; while (!cycle.isEmpty()) { Node endOfCycle = cycle.getLast(); if (endOfCycle.targets.isEmpty()) { cycle.removeLast(); isInCycle[endOfCycle.index] = false; if (!cycle.isEmpty()) { cycle.getLast().targets.removeFirst(); } } else { Node nextInCycle = endOfCycle.targets.getFirst(); if (isInCycle[nextInCycle.index]) { while (cycle.getFirst() != nextInCycle) { cycle.removeFirst(); } return cycle; } else { cycle.add(nextInCycle); isInCycle[nextInCycle.index] = true; } } } } return null; } private static class Node { int index; LinkedList<Node> targets = new LinkedList<>(); public Node(int index) { this.index = index; } public String toString() { return "" + index; } } private static class FastScanner { private final InputStream stream; private final byte[] buf = new byte[1024]; private int curChar; private int numChars; private SpaceCharFilter filter; public FastScanner(InputStream stream) { this.stream = stream; } public int read() { if (numChars == -1) { throw new InputMismatchException(); } if (curChar >= numChars) { curChar = 0; try { numChars = stream.read(buf); } catch (IOException e) { throw new InputMismatchException(); } if (numChars <= 0) { return -1; } } return buf[curChar++]; } public int nextInt() { int c = read(); while (isSpaceChar(c)) { c = read(); } int sgn = 1; if (c == '-') { sgn = -1; c = read(); } int res = 0; do { if (c < '0' || c > '9') { throw new InputMismatchException(); } res *= 10; res += c - '0'; c = read(); } while (!isSpaceChar(c)); return res * sgn; } public boolean isSpaceChar(int c) { if (filter != null) { return filter.isSpaceChar(c); } return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; } public interface SpaceCharFilter { public boolean isSpaceChar(int ch); } } }
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 | import java.io.IOException; import java.io.InputStream; import java.util.InputMismatchException; import java.util.Iterator; import java.util.LinkedList; public class kon { private static int highestNodeIndex; public static void main(String... args) { FastScanner scanner = new FastScanner(System.in); highestNodeIndex = scanner.nextInt(); int numberOfLines = scanner.nextInt(); Node[] nodes = new Node[highestNodeIndex + 1]; LinkedList<Node> graph = new LinkedList<>(); for (int index = 1; index <= highestNodeIndex; index++) { Node node = new Node(index); nodes[index] = node; graph.add(node); } for (int i = 0; i < numberOfLines; i++) { Node source = nodes[scanner.nextInt()]; Node target = nodes[scanner.nextInt()]; source.targets.add(target); } LinkedList<Node> cycle = findCycle(graph); if (cycle == null) { System.out.println("NIE"); return; } LinkedList<Integer> hubs = findHubs(cycle, graph); if (hubs.isEmpty()) { printHubs(hubs); return; } for (Integer hub : hubs) { nodes[hub].targets.clear(); } cycle = findCycle(graph); if (cycle == null) { printHubs(hubs); return; } else { printHubs(new LinkedList<Integer>()); } } private static void printHubs(LinkedList<Integer> hubs) { System.out.println(hubs.size()); Iterator<Integer> iterator = hubs.iterator(); if (iterator.hasNext()) { System.out.print(iterator.next()); } while (iterator.hasNext()) { System.out.print(" "); System.out.print(iterator.next()); } System.out.println(); } private static LinkedList<Integer> findHubs(LinkedList<Node> cycle, LinkedList<Node> graph) { boolean[] isInCycle = new boolean[highestNodeIndex + 1]; boolean[] isInPath = new boolean[highestNodeIndex + 1]; int[] isClouded = new int[highestNodeIndex + 1]; boolean[] canBeDetoured = new boolean[highestNodeIndex + 1]; for (Node cycleNode : cycle) { isInCycle[cycleNode.index] = true; } LinkedList<Node> cloudStarters = new LinkedList<>(cycle); int numberOfDetours = 0; boolean[] isDetourEnd = new boolean[highestNodeIndex + 1]; while (!cloudStarters.isEmpty()) { Node cloudStarter = cloudStarters.removeFirst(); if (isDetourEnd[cloudStarter.index]) { isDetourEnd[cloudStarter.index] = false; numberOfDetours--; } if (numberOfDetours > 0) { canBeDetoured[cloudStarter.index] = true; } LinkedList<Node> path = new LinkedList<Node>(); path.add(cloudStarter); isInPath[cloudStarter.index] = true; while (!path.isEmpty()) { Node tail = path.getLast(); if (!tail.targets.isEmpty()) { Node target = tail.targets.removeLast(); if (isInCycle[target.index]) { if (!isDetourEnd[target.index]) { isDetourEnd[target.index] = true; numberOfDetours++; } isClouded[tail.index] = target.index; } else if (isInPath[target.index]) { // another cycle!!! return new LinkedList<Integer>(); } else if (isClouded[target.index] != 0) { int cloudedBy = isClouded[target.index]; isClouded[tail.index] = cloudedBy; if (!isDetourEnd[cloudedBy]) { isDetourEnd[cloudedBy] = true; numberOfDetours++; } } else { isInPath[target.index] = true; path.add(target); } } else { isInPath[tail.index] = false; path.removeLast(); } } } for (Node cycleNode : cycle) { if (numberOfDetours > 0) { if (isDetourEnd[cycleNode.index]) { isDetourEnd[cycleNode.index] = false; numberOfDetours--; } } if (numberOfDetours > 0) { canBeDetoured[cycleNode.index] = true; } else { break; } } LinkedList<Integer> hubs = new LinkedList<>(); for (int i = 1; i <= highestNodeIndex; i++) { if (isInCycle[i] && !canBeDetoured[i]) { hubs.add(i); } } return hubs; } private static LinkedList<Node> findCycle(LinkedList<Node> graph) { LinkedList<Node> startCandidates = new LinkedList<>(graph); while (!startCandidates.isEmpty()) { LinkedList<Node> cycle = new LinkedList<>(); boolean[] isInCycle = new boolean[highestNodeIndex + 1]; cycle.add(startCandidates.removeFirst()); isInCycle[cycle.getFirst().index] = true; while (!cycle.isEmpty()) { Node endOfCycle = cycle.getLast(); if (endOfCycle.targets.isEmpty()) { cycle.removeLast(); isInCycle[endOfCycle.index] = false; if (!cycle.isEmpty()) { cycle.getLast().targets.removeFirst(); } } else { Node nextInCycle = endOfCycle.targets.getFirst(); if (isInCycle[nextInCycle.index]) { while (cycle.getFirst() != nextInCycle) { cycle.removeFirst(); } return cycle; } else { cycle.add(nextInCycle); isInCycle[nextInCycle.index] = true; } } } } return null; } private static class Node { int index; LinkedList<Node> targets = new LinkedList<>(); public Node(int index) { this.index = index; } public String toString() { return "" + index; } } private static class FastScanner { private final InputStream stream; private final byte[] buf = new byte[1024]; private int curChar; private int numChars; private SpaceCharFilter filter; public FastScanner(InputStream stream) { this.stream = stream; } public int read() { if (numChars == -1) { throw new InputMismatchException(); } if (curChar >= numChars) { curChar = 0; try { numChars = stream.read(buf); } catch (IOException e) { throw new InputMismatchException(); } if (numChars <= 0) { return -1; } } return buf[curChar++]; } public int nextInt() { int c = read(); while (isSpaceChar(c)) { c = read(); } int sgn = 1; if (c == '-') { sgn = -1; c = read(); } int res = 0; do { if (c < '0' || c > '9') { throw new InputMismatchException(); } res *= 10; res += c - '0'; c = read(); } while (!isSpaceChar(c)); return res * sgn; } public boolean isSpaceChar(int c) { if (filter != null) { return filter.isSpaceChar(c); } return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; } public interface SpaceCharFilter { public boolean isSpaceChar(int ch); } } } |