#include <cstdio> #include <cstring> #include <iostream> #include <vector> using namespace std; static const unsigned long CON_MAX_N = 500001; static const unsigned long CON_MAX_M = 1000000; static long gEdges[2*CON_MAX_M]; static long gEdgesBuf[CON_MAX_M]; struct SNode { long nEdges; bool bInAllCycles; bool bVisited; bool bInPath; long *pEdges; SNode() : nEdges(0), bInAllCycles(true), bVisited(false), bInPath(false), pEdges(NULL) {} }; static unsigned long gGraphSize, gResult; static SNode gGraph[CON_MAX_N]; static bool gbInCycle[CON_MAX_N]; struct SStackNode { long num; long egdeIdx; SStackNode(long n) : num(n), egdeIdx(0){} }; bool dfs(unsigned long start) // wglab { vector<SStackNode> dfsStack; bool res = false; unsigned long idx; gGraph[start].bVisited = true; gGraph[start].bInPath = true; dfsStack.push_back(SStackNode(start)); while(!dfsStack.empty()) { SStackNode &curr = dfsStack.back(); if (curr.egdeIdx == gGraph[curr.num].nEdges) { dfsStack.pop_back(); gGraph[curr.num].bInPath = false; continue; } while (curr.egdeIdx < gGraph[curr.num].nEdges) { unsigned long next = gGraph[curr.num].pEdges[curr.egdeIdx]; ++ curr.egdeIdx; if(!gGraph[next].bInPath) { gGraph[next].bVisited = true; gGraph[next].bInPath = true; dfsStack.push_back(SStackNode(next)); break; } else { memset(gbInCycle, 0, sizeof(gbInCycle)); for(idx = 0; idx < dfsStack.size() && dfsStack[idx].num != next; ++ idx); for(; idx < dfsStack.size(); ++ idx) { gbInCycle[dfsStack[idx].num] = true; } for(idx = 1; idx <= gGraphSize; ++ idx) { if(gGraph[idx].bInAllCycles && !gbInCycle[idx]) { -- gResult; } gGraph[idx].bInAllCycles = (gGraph[idx].bInAllCycles && gbInCycle[idx]); } if(gResult == 0) { return true; } res = true; } } } return res; } int main() { bool bIsCycle = false; unsigned long M, i, idx = 0; cin >> gGraphSize >> M; gResult = gGraphSize; for(i = 0; i < M*2; i += 2) { cin >> gEdges[i] >> gEdges[i+1]; ++ gGraph[gEdges[i]].nEdges; } for(i = 1; i <= gGraphSize; ++i) { gGraph[i].pEdges = &gEdgesBuf[idx]; idx += gGraph[i].nEdges; gGraph[i].nEdges = 0; } for(i = 0; i < M*2; i += 2) { gGraph[gEdges[i]].pEdges[gGraph[gEdges[i]].nEdges] = gEdges[i+1]; ++ gGraph[gEdges[i]].nEdges; } for(i = 1; i <= gGraphSize; ++i) { if(!gGraph[i].bVisited && dfs(i)) { bIsCycle = true; if(gResult == 0) { break; } } } if(bIsCycle) { cout << gResult << endl; if(gResult > 0) { for(i = 1; i <= gGraphSize; ++i) { if(gGraph[i].bInAllCycles) { cout << i << " "; } } } } else { cout << "NIE"; } }
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 | #include <cstdio> #include <cstring> #include <iostream> #include <vector> using namespace std; static const unsigned long CON_MAX_N = 500001; static const unsigned long CON_MAX_M = 1000000; static long gEdges[2*CON_MAX_M]; static long gEdgesBuf[CON_MAX_M]; struct SNode { long nEdges; bool bInAllCycles; bool bVisited; bool bInPath; long *pEdges; SNode() : nEdges(0), bInAllCycles(true), bVisited(false), bInPath(false), pEdges(NULL) {} }; static unsigned long gGraphSize, gResult; static SNode gGraph[CON_MAX_N]; static bool gbInCycle[CON_MAX_N]; struct SStackNode { long num; long egdeIdx; SStackNode(long n) : num(n), egdeIdx(0){} }; bool dfs(unsigned long start) // wglab { vector<SStackNode> dfsStack; bool res = false; unsigned long idx; gGraph[start].bVisited = true; gGraph[start].bInPath = true; dfsStack.push_back(SStackNode(start)); while(!dfsStack.empty()) { SStackNode &curr = dfsStack.back(); if (curr.egdeIdx == gGraph[curr.num].nEdges) { dfsStack.pop_back(); gGraph[curr.num].bInPath = false; continue; } while (curr.egdeIdx < gGraph[curr.num].nEdges) { unsigned long next = gGraph[curr.num].pEdges[curr.egdeIdx]; ++ curr.egdeIdx; if(!gGraph[next].bInPath) { gGraph[next].bVisited = true; gGraph[next].bInPath = true; dfsStack.push_back(SStackNode(next)); break; } else { memset(gbInCycle, 0, sizeof(gbInCycle)); for(idx = 0; idx < dfsStack.size() && dfsStack[idx].num != next; ++ idx); for(; idx < dfsStack.size(); ++ idx) { gbInCycle[dfsStack[idx].num] = true; } for(idx = 1; idx <= gGraphSize; ++ idx) { if(gGraph[idx].bInAllCycles && !gbInCycle[idx]) { -- gResult; } gGraph[idx].bInAllCycles = (gGraph[idx].bInAllCycles && gbInCycle[idx]); } if(gResult == 0) { return true; } res = true; } } } return res; } int main() { bool bIsCycle = false; unsigned long M, i, idx = 0; cin >> gGraphSize >> M; gResult = gGraphSize; for(i = 0; i < M*2; i += 2) { cin >> gEdges[i] >> gEdges[i+1]; ++ gGraph[gEdges[i]].nEdges; } for(i = 1; i <= gGraphSize; ++i) { gGraph[i].pEdges = &gEdgesBuf[idx]; idx += gGraph[i].nEdges; gGraph[i].nEdges = 0; } for(i = 0; i < M*2; i += 2) { gGraph[gEdges[i]].pEdges[gGraph[gEdges[i]].nEdges] = gEdges[i+1]; ++ gGraph[gEdges[i]].nEdges; } for(i = 1; i <= gGraphSize; ++i) { if(!gGraph[i].bVisited && dfs(i)) { bIsCycle = true; if(gResult == 0) { break; } } } if(bIsCycle) { cout << gResult << endl; if(gResult > 0) { for(i = 1; i <= gGraphSize; ++i) { if(gGraph[i].bInAllCycles) { cout << i << " "; } } } } else { cout << "NIE"; } } |