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Johnson's algorithm - Finding All the Elementary Circuits of a Directed Graph
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| #include <algorithm> | |
| #include <cstdio> | |
| #include <type_traits> | |
| #include <vector> | |
| using namespace std; | |
| #define ALL(x) (x).begin(), (x).end() | |
| #define FOR(i, a, b) for (remove_cv<remove_reference<decltype(b)>::type>::type i = (a); i < (b); i++) | |
| #define REP(i, n) FOR(i, 0, n) | |
| int ri() { | |
| int x; | |
| scanf("%d", &x); | |
| return x; | |
| } | |
| vector<int> vis; | |
| vector<char> blocked; | |
| vector<vector<int>> es, closed; | |
| void unblock(int u) { | |
| blocked[u] = false; | |
| for (int v: closed[u]) | |
| if (blocked[v]) | |
| unblock(v); | |
| } | |
| bool johnson_cycle(int u, int src) { | |
| bool found = false; | |
| vis.push_back(u); | |
| blocked[u] = true; | |
| for (int v : es[u]) | |
| if (v == src) { | |
| for (int w: vis) | |
| printf("%d ", w); | |
| puts(""); | |
| found = true; | |
| } else if (!blocked[v]) | |
| found |= johnson_cycle(v, src); | |
| if (found) | |
| unblock(u); | |
| else | |
| for (int v: es[u]) | |
| if (v >= src) { | |
| auto &c = closed[u]; | |
| if (find(ALL(c), v) == c.end()) | |
| c.push_back(v); | |
| } | |
| vis.pop_back(); | |
| return found; | |
| } | |
| int main() { | |
| int n = ri(), v; | |
| es.resize(n); | |
| REP(i, n) | |
| for (int k = ri(); k--; ) | |
| es[i].push_back(ri()); | |
| blocked.resize(n); | |
| closed.resize(n); | |
| REP(i, n) { | |
| fill(blocked.begin()+i, blocked.end(), false); | |
| johnson_cycle(i, i); | |
| blocked[i] = true; | |
| } | |
| } | |
| /* | |
| (0,1) (0,2) (1,0) (1,2) (2,0) (2,3) (3,1) | |
| input: | |
| 4 | |
| 2 1 2 | |
| 2 0 2 | |
| 2 0 3 | |
| 1 1 | |
| */ |
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