#include <iostream> #include <vector> #include <stack> #define N_MAX 200002 using namespace std; struct vertex : public vector<int> { enum state_t { notVisited, inDfs, visited }; state_t state; unsigned int inCycles; int parent; }; class graph_t { public: graph_t() : cyclesFound(0), V(N_MAX), cycleIsles(0) {} unsigned int numVertices, numEdges, cyclesFound; vector<vertex> V; int cycleIsles; void addEdge(int a, int b) { V[a].push_back(b); } void dfs(int v) { //cout << "DFSing vertex " << v+1 << endl; bool cycleFound = false; stack<int> s; s.push(v); while (!s.empty()) { int x; v = s.top(); if (V[v].state == vertex::notVisited) { //out << " Visiting vertex " << v + 1 << endl; V[v].state = vertex::inDfs; } else // vertex::inDfs { //cout << " Exiting vertex " << v + 1 << endl; V[v].state = vertex::visited; s.pop(); continue; } for (vertex::iterator it = V[v].begin(); it != V[v].end(); ++it) { if (V[*it].state == vertex::notVisited) { s.push(*it); V[*it].parent = v; } else if (V[*it].state == vertex::inDfs) { //cout << "Cycle found, " << v + 1 << " -> " << *it + 1 << endl; if (!cycleFound) cycleFound = true; ++cyclesFound; x = v; while ( x != *it) { ++(V[x].inCycles); //cout << " " << x+1 << " is there" << endl; x = V[x].parent; } ++(V[x].inCycles); // ostatni trzeba ręcznie //cout << " " << x+1 << " is there" << endl; } } } if (cycleFound) ++cycleIsles; //cout << "isles: " << cycleIsles << endl;} } void printInAllCycles() { int goodNum = 0; vector<int> good; for (unsigned int i = 0; i < numVertices; ++i) { if ( V[i].inCycles == cyclesFound) // in all cycles { ++goodNum; good.push_back(i+1); } } cout << goodNum << "\n"; for (vector<int>::iterator it = good.begin(); it != good.end(); ++it) { cout << *it << " "; } } }; graph_t graph; int a,b; int main() { ios_base::sync_with_stdio(false); cin >> graph.numVertices >> graph.numEdges; for (unsigned int i = 0; i < graph.numEdges; ++i) { //cout << i+1 << " out of " << graph.numEdges << "\n"; cin >> a >> b; graph.addEdge(a-1,b-1); } //cout << "done!" << endl; for (unsigned int i = 0; i < graph.numVertices; ++i) { if (graph.V[i].state == vertex::notVisited) graph.dfs(i); if (graph.cycleIsles > 1) { cout << "0\n"; return 0; } } //cout << "==================" << endl; if (graph.cyclesFound == 0) { cout << "NIE\n"; return 0; } else { graph.printInAllCycles(); } 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 | #include <iostream> #include <vector> #include <stack> #define N_MAX 200002 using namespace std; struct vertex : public vector<int> { enum state_t { notVisited, inDfs, visited }; state_t state; unsigned int inCycles; int parent; }; class graph_t { public: graph_t() : cyclesFound(0), V(N_MAX), cycleIsles(0) {} unsigned int numVertices, numEdges, cyclesFound; vector<vertex> V; int cycleIsles; void addEdge(int a, int b) { V[a].push_back(b); } void dfs(int v) { //cout << "DFSing vertex " << v+1 << endl; bool cycleFound = false; stack<int> s; s.push(v); while (!s.empty()) { int x; v = s.top(); if (V[v].state == vertex::notVisited) { //out << " Visiting vertex " << v + 1 << endl; V[v].state = vertex::inDfs; } else // vertex::inDfs { //cout << " Exiting vertex " << v + 1 << endl; V[v].state = vertex::visited; s.pop(); continue; } for (vertex::iterator it = V[v].begin(); it != V[v].end(); ++it) { if (V[*it].state == vertex::notVisited) { s.push(*it); V[*it].parent = v; } else if (V[*it].state == vertex::inDfs) { //cout << "Cycle found, " << v + 1 << " -> " << *it + 1 << endl; if (!cycleFound) cycleFound = true; ++cyclesFound; x = v; while ( x != *it) { ++(V[x].inCycles); //cout << " " << x+1 << " is there" << endl; x = V[x].parent; } ++(V[x].inCycles); // ostatni trzeba ręcznie //cout << " " << x+1 << " is there" << endl; } } } if (cycleFound) ++cycleIsles; //cout << "isles: " << cycleIsles << endl;} } void printInAllCycles() { int goodNum = 0; vector<int> good; for (unsigned int i = 0; i < numVertices; ++i) { if ( V[i].inCycles == cyclesFound) // in all cycles { ++goodNum; good.push_back(i+1); } } cout << goodNum << "\n"; for (vector<int>::iterator it = good.begin(); it != good.end(); ++it) { cout << *it << " "; } } }; graph_t graph; int a,b; int main() { ios_base::sync_with_stdio(false); cin >> graph.numVertices >> graph.numEdges; for (unsigned int i = 0; i < graph.numEdges; ++i) { //cout << i+1 << " out of " << graph.numEdges << "\n"; cin >> a >> b; graph.addEdge(a-1,b-1); } //cout << "done!" << endl; for (unsigned int i = 0; i < graph.numVertices; ++i) { if (graph.V[i].state == vertex::notVisited) graph.dfs(i); if (graph.cycleIsles > 1) { cout << "0\n"; return 0; } } //cout << "==================" << endl; if (graph.cyclesFound == 0) { cout << "NIE\n"; return 0; } else { graph.printInAllCycles(); } return 0; } |