#include <bits/stdc++.h> #define forn(i, n) for(int i = 0; i < n; ++i) using namespace std; typedef long long LL; typedef pair<int, int> pint; int n,m,k; vector<int> nbh[342]; set<int> inverts[342]; int mincmp = 1000000; set<vector<int>> was; int cmp[342]; int par[342]; int indeg[342]; void bfs(int v1, int v2, int v3, int v4) { queue<int> Q; for (int i=1; i<=n; i++) { if (i == v1 || i == v2 || i == v3 || i == v4) { par[i] = -1; cmp[i] = 0; continue; } par[i] = -1; cmp[i] = 1; int s = inverts[i].size(); s -= (inverts[i].find(v1) != inverts[i].end()); s -= (inverts[i].find(v2) != inverts[i].end()); s -= (inverts[i].find(v3) != inverts[i].end()); s -= (inverts[i].find(v4) != inverts[i].end()); if (s == 0) Q.push(i); indeg[i] = s; } while (!Q.empty()) { int a = Q.front(); Q.pop(); for (int v : nbh[a]) { if (v == v1 || v == v2 || v == v3 || v == v4) continue; indeg[v]--; cmp[v] = max(cmp[v],cmp[a]+1); if (indeg[v] == 0) { par[v] = a; Q.push(v); } } } } void solve(int k, int v1 = -1, int v2 = -1, int v3 = -1, int v4 = -1) { vector<int> vv = {v1,v2,v3,v4}; sort(vv.begin(),vv.end()); if (was.find(vv) != was.end()) return; was.insert(vv); bfs(v1,v2,v3,v4); if (k == 0) { int maxcmp = 0; for (int i=1; i<=n; i++) { if (maxcmp < cmp[i] && i != v1 && i != v2 && i != v3 && i != v4) maxcmp = cmp[i]; } mincmp = min(mincmp, maxcmp); return; } int vmaxcmp = 0; for (int i=1; i<=n; i++) { if (cmp[i] > cmp[vmaxcmp]) vmaxcmp = i; } if (cmp[vmaxcmp] < mincmp) mincmp = cmp[vmaxcmp]; vector<int> to_erase; while (vmaxcmp != -1) { to_erase.push_back(vmaxcmp); vmaxcmp = par[vmaxcmp]; } for (int v : to_erase) { if (v1 == -1) solve(k-1, v); else if (v2 == -1) solve(k-1, v1, v); else if (v3 == -1) solve(k-1, v1, v2, v); else solve(k-1, v1, v2, v3, v); } } int main() { ios_base::sync_with_stdio(false); cin.tie(0); cin >> n >> m >> k; for (int i=0; i<m; i++) { int x,y; cin >> x >> y; nbh[x].push_back(y); inverts[y].insert(x); } solve(k); cout << mincmp; 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 | #include <bits/stdc++.h> #define forn(i, n) for(int i = 0; i < n; ++i) using namespace std; typedef long long LL; typedef pair<int, int> pint; int n,m,k; vector<int> nbh[342]; set<int> inverts[342]; int mincmp = 1000000; set<vector<int>> was; int cmp[342]; int par[342]; int indeg[342]; void bfs(int v1, int v2, int v3, int v4) { queue<int> Q; for (int i=1; i<=n; i++) { if (i == v1 || i == v2 || i == v3 || i == v4) { par[i] = -1; cmp[i] = 0; continue; } par[i] = -1; cmp[i] = 1; int s = inverts[i].size(); s -= (inverts[i].find(v1) != inverts[i].end()); s -= (inverts[i].find(v2) != inverts[i].end()); s -= (inverts[i].find(v3) != inverts[i].end()); s -= (inverts[i].find(v4) != inverts[i].end()); if (s == 0) Q.push(i); indeg[i] = s; } while (!Q.empty()) { int a = Q.front(); Q.pop(); for (int v : nbh[a]) { if (v == v1 || v == v2 || v == v3 || v == v4) continue; indeg[v]--; cmp[v] = max(cmp[v],cmp[a]+1); if (indeg[v] == 0) { par[v] = a; Q.push(v); } } } } void solve(int k, int v1 = -1, int v2 = -1, int v3 = -1, int v4 = -1) { vector<int> vv = {v1,v2,v3,v4}; sort(vv.begin(),vv.end()); if (was.find(vv) != was.end()) return; was.insert(vv); bfs(v1,v2,v3,v4); if (k == 0) { int maxcmp = 0; for (int i=1; i<=n; i++) { if (maxcmp < cmp[i] && i != v1 && i != v2 && i != v3 && i != v4) maxcmp = cmp[i]; } mincmp = min(mincmp, maxcmp); return; } int vmaxcmp = 0; for (int i=1; i<=n; i++) { if (cmp[i] > cmp[vmaxcmp]) vmaxcmp = i; } if (cmp[vmaxcmp] < mincmp) mincmp = cmp[vmaxcmp]; vector<int> to_erase; while (vmaxcmp != -1) { to_erase.push_back(vmaxcmp); vmaxcmp = par[vmaxcmp]; } for (int v : to_erase) { if (v1 == -1) solve(k-1, v); else if (v2 == -1) solve(k-1, v1, v); else if (v3 == -1) solve(k-1, v1, v2, v); else solve(k-1, v1, v2, v3, v); } } int main() { ios_base::sync_with_stdio(false); cin.tie(0); cin >> n >> m >> k; for (int i=0; i<m; i++) { int x,y; cin >> x >> y; nbh[x].push_back(y); inverts[y].insert(x); } solve(k); cout << mincmp; return 0; } |