#include<cstdio> #include<algorithm> #include<utility> #include<string> #include<vector> #include<map> #include<set> #include<queue> #include<stack> #include<cmath> #include<iostream> #define FORE(c, a, b) for(int c=a; c<= int(b); ++c) #define FORD(c, a, b) for(int c=a; c>= int(b); --c) #define FORIT(it, cont, cont_t) for(cont_t::iterator it = cont.begin(); it != cont.end(); ++it) #define REP(i, n) for(int i = 0; i < (n); ++i) #define ALL(a) a.begin(), a.end() #define PR(n) printf("%d ", (int) (n)) #define PRL(n) printf("%lld ", (ll) (n)) #define SC(n) scanf("%d ", &n) #define xx first #define yy second #define pb push_back #define mp make_pair #define itr iterator #define dbg if(0) #define prd dbg printf using namespace std; typedef long long ll; typedef long double ld; typedef unsigned int uint; typedef vector<int> vi; typedef map<int, int> mi; typedef pair<int, int> pi; typedef pair<int, pi> pii; typedef vector<pi> vii; typedef vector<pii> vpii; typedef set<int> si; typedef set<pi> spi; const int NMAX = 600 * 1000 + 9; int n, m, x, y, k; int isCycle, vis[NMAX], cyclePos[NMAX], minPos[NMAX], f[NMAX]; vi edges[NMAX], cycle, ans; int isShifted(vi & a, vi & b) { // taki sam size if(a.empty()) return 1; int i = 0, aa = a.size(); while(i < aa && a[i] != b[0]) i++; if(i == aa) return 0; REP(j, aa) { int jj = j + i; jj = jj >= aa ? jj - aa : jj; if(a[jj] != b[j]) return 0; } return 1; } int myDist(int a, int b) { a = a + k - b; return a >= k ? a - k : a; } int myRet(int v, int w) { prd("add %d\n", v); cycle.pb(v); vis[v] = 2; return w; } int dfs_cycle(int v) { // -1: finish, NMAX: no cycle, w: unfolding started in w prd("dfs_cycle %d\n", v); vis[v] = 1; FORIT(it, edges[v], vi) { int w = *it; if(vis[w] == 1) { return myRet(v, w); } else if(vis[w] == 2) continue; int ret = dfs_cycle(w); if(ret == -1) { vis[v] = 2; return -1; } else if(ret == v) { return myRet(v, -1); } else if(ret < NMAX) { return myRet(v, ret); } // if NMAX go on } vis[v] = 2; return NMAX; } void update(int & xv, int xw, int start) { prd("update %d %d %d = ", xv, xw, start); if(xv == -1 || xw == NMAX) return; if(xw == -1 || xv == NMAX) xv = xw; else xv = myDist(xw, start) < myDist(xv, start) ? xw : xv; } void dfs_afap(int v, int start) { prd("dfs_afap %d (%d) \n", v, start); if(cyclePos[v] >= 0 && cyclePos[v] != start) return; vis[v] = 1; minPos[v] = NMAX; FORIT(it, edges[v], vi) { int w = *it; if(vis[w] == 1) { if(cyclePos[w] >= 0) { // doszedlem so siebie if(cyclePos[w] != start) prd("ALERT SHIT\n"); } else { // znalazlem niezalezny cykl prd("found cycle\n"); minPos[v] = -1; } } if(vis[w] == 0) dfs_afap(w, start); update(minPos[v], cyclePos[w] >= 0 ? cyclePos[w] : minPos[w], start); prd("%d\n", minPos[v]); } prd("minPos[%d] = %d\n", v, minPos[v]); vis[v] = 2; } int dfs_tree(int v) { prd("dfs_tree %d\n", v); // -1: finish, NMAX: no cycle, w: unfolding started in w vis[v] = 1; if(vis[f[v]] == 1) { prd("ans: %d\n", cycle[v]); ans.clear(); // olewamy poprzedni i tak wyjdzie zaraz ze sa 2 ans.pb(cycle[v]); vis[v] = 2; return v == f[v] ? -1 : f[v]; } if(vis[f[v]] == 2) { vis[v] = 2; return NMAX; } int ret = dfs_tree(f[v]); vis[v] = 2; if(ret == -1 || ret == NMAX) return ret; if(ret == v) ret = -1; prd("ans: %d\n", cycle[v]); ans.pb(cycle[v]); return ret; } int cycleToAns() { // wystarcza wierzcholki od konca na vi: cycle FORE(i, 1, n) { vis[i] = 0; cyclePos[i] = -1; } REP(ci, cycle.size()) cyclePos[cycle[ci]] = ci; k = cycle.size(); // oblicz f dla [0, k) REP(ci, cycle.size()) { // cykl jest od konca int cand = cycle[ci]; prd("cand %d\n", cand); dfs_afap(cand, ci); if(minPos[cand] == -1) return 1; f[ci] = minPos[cand]; prd("f[%d] = %d\n", ci, f[ci]); } // oblicz cykl dla f ans.clear(); REP(i, k) { prd("f[%d] = %d g[%d] = %d\n", i, f[i], cycle[i], cycle[f[i]]); vis[i] = 0; } REP(i, k) if(!vis[i]) dfs_tree(i); return 0; } int main() { scanf("%d%d", &n, &m); REP(i, m) { scanf("%d%d", &x, &y); edges[x].pb(y); } // znajdz initial cycle FORE(i, 1, n) vis[i] = 0; FORE(i, 1, n) if(cycle.empty() && !vis[i]) dfs_cycle(i); if(cycle.empty()) { printf("NIE"); return 0; } while(1) { if(cycleToAns()) { printf("0\n\n"); return 0; } /*FORIT(it, ans, vi) printf("%d ", *it); printf("(%d %d %d)\n", (int) ans.size(), (int) cycle.size(), isShifted(ans, cycle));*/ if(ans.size() == cycle.size()) { if(isShifted(ans, cycle)) break; else { printf("0\n\n"); return 0; } } cycle = ans; } // sprawdz czy nie ma jakiegos drugiego cyklu FORE(i, 1, n) vis[i] = 0; FORIT(it, ans, vi) vis[*it] = 2; cycle.clear(); FORE(i, 1, n) if(!vis[i]) dfs_cycle(i); if(!cycle.empty()) { printf("0\n\n"); return 0; } sort(ALL(ans)); printf("%d\n", (int) ans.size()); FORIT(it, ans, vi) printf("%d ", *it); 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 | #include<cstdio> #include<algorithm> #include<utility> #include<string> #include<vector> #include<map> #include<set> #include<queue> #include<stack> #include<cmath> #include<iostream> #define FORE(c, a, b) for(int c=a; c<= int(b); ++c) #define FORD(c, a, b) for(int c=a; c>= int(b); --c) #define FORIT(it, cont, cont_t) for(cont_t::iterator it = cont.begin(); it != cont.end(); ++it) #define REP(i, n) for(int i = 0; i < (n); ++i) #define ALL(a) a.begin(), a.end() #define PR(n) printf("%d ", (int) (n)) #define PRL(n) printf("%lld ", (ll) (n)) #define SC(n) scanf("%d ", &n) #define xx first #define yy second #define pb push_back #define mp make_pair #define itr iterator #define dbg if(0) #define prd dbg printf using namespace std; typedef long long ll; typedef long double ld; typedef unsigned int uint; typedef vector<int> vi; typedef map<int, int> mi; typedef pair<int, int> pi; typedef pair<int, pi> pii; typedef vector<pi> vii; typedef vector<pii> vpii; typedef set<int> si; typedef set<pi> spi; const int NMAX = 600 * 1000 + 9; int n, m, x, y, k; int isCycle, vis[NMAX], cyclePos[NMAX], minPos[NMAX], f[NMAX]; vi edges[NMAX], cycle, ans; int isShifted(vi & a, vi & b) { // taki sam size if(a.empty()) return 1; int i = 0, aa = a.size(); while(i < aa && a[i] != b[0]) i++; if(i == aa) return 0; REP(j, aa) { int jj = j + i; jj = jj >= aa ? jj - aa : jj; if(a[jj] != b[j]) return 0; } return 1; } int myDist(int a, int b) { a = a + k - b; return a >= k ? a - k : a; } int myRet(int v, int w) { prd("add %d\n", v); cycle.pb(v); vis[v] = 2; return w; } int dfs_cycle(int v) { // -1: finish, NMAX: no cycle, w: unfolding started in w prd("dfs_cycle %d\n", v); vis[v] = 1; FORIT(it, edges[v], vi) { int w = *it; if(vis[w] == 1) { return myRet(v, w); } else if(vis[w] == 2) continue; int ret = dfs_cycle(w); if(ret == -1) { vis[v] = 2; return -1; } else if(ret == v) { return myRet(v, -1); } else if(ret < NMAX) { return myRet(v, ret); } // if NMAX go on } vis[v] = 2; return NMAX; } void update(int & xv, int xw, int start) { prd("update %d %d %d = ", xv, xw, start); if(xv == -1 || xw == NMAX) return; if(xw == -1 || xv == NMAX) xv = xw; else xv = myDist(xw, start) < myDist(xv, start) ? xw : xv; } void dfs_afap(int v, int start) { prd("dfs_afap %d (%d) \n", v, start); if(cyclePos[v] >= 0 && cyclePos[v] != start) return; vis[v] = 1; minPos[v] = NMAX; FORIT(it, edges[v], vi) { int w = *it; if(vis[w] == 1) { if(cyclePos[w] >= 0) { // doszedlem so siebie if(cyclePos[w] != start) prd("ALERT SHIT\n"); } else { // znalazlem niezalezny cykl prd("found cycle\n"); minPos[v] = -1; } } if(vis[w] == 0) dfs_afap(w, start); update(minPos[v], cyclePos[w] >= 0 ? cyclePos[w] : minPos[w], start); prd("%d\n", minPos[v]); } prd("minPos[%d] = %d\n", v, minPos[v]); vis[v] = 2; } int dfs_tree(int v) { prd("dfs_tree %d\n", v); // -1: finish, NMAX: no cycle, w: unfolding started in w vis[v] = 1; if(vis[f[v]] == 1) { prd("ans: %d\n", cycle[v]); ans.clear(); // olewamy poprzedni i tak wyjdzie zaraz ze sa 2 ans.pb(cycle[v]); vis[v] = 2; return v == f[v] ? -1 : f[v]; } if(vis[f[v]] == 2) { vis[v] = 2; return NMAX; } int ret = dfs_tree(f[v]); vis[v] = 2; if(ret == -1 || ret == NMAX) return ret; if(ret == v) ret = -1; prd("ans: %d\n", cycle[v]); ans.pb(cycle[v]); return ret; } int cycleToAns() { // wystarcza wierzcholki od konca na vi: cycle FORE(i, 1, n) { vis[i] = 0; cyclePos[i] = -1; } REP(ci, cycle.size()) cyclePos[cycle[ci]] = ci; k = cycle.size(); // oblicz f dla [0, k) REP(ci, cycle.size()) { // cykl jest od konca int cand = cycle[ci]; prd("cand %d\n", cand); dfs_afap(cand, ci); if(minPos[cand] == -1) return 1; f[ci] = minPos[cand]; prd("f[%d] = %d\n", ci, f[ci]); } // oblicz cykl dla f ans.clear(); REP(i, k) { prd("f[%d] = %d g[%d] = %d\n", i, f[i], cycle[i], cycle[f[i]]); vis[i] = 0; } REP(i, k) if(!vis[i]) dfs_tree(i); return 0; } int main() { scanf("%d%d", &n, &m); REP(i, m) { scanf("%d%d", &x, &y); edges[x].pb(y); } // znajdz initial cycle FORE(i, 1, n) vis[i] = 0; FORE(i, 1, n) if(cycle.empty() && !vis[i]) dfs_cycle(i); if(cycle.empty()) { printf("NIE"); return 0; } while(1) { if(cycleToAns()) { printf("0\n\n"); return 0; } /*FORIT(it, ans, vi) printf("%d ", *it); printf("(%d %d %d)\n", (int) ans.size(), (int) cycle.size(), isShifted(ans, cycle));*/ if(ans.size() == cycle.size()) { if(isShifted(ans, cycle)) break; else { printf("0\n\n"); return 0; } } cycle = ans; } // sprawdz czy nie ma jakiegos drugiego cyklu FORE(i, 1, n) vis[i] = 0; FORIT(it, ans, vi) vis[*it] = 2; cycle.clear(); FORE(i, 1, n) if(!vis[i]) dfs_cycle(i); if(!cycle.empty()) { printf("0\n\n"); return 0; } sort(ALL(ans)); printf("%d\n", (int) ans.size()); FORIT(it, ans, vi) printf("%d ", *it); return 0; } |