#include <bits/stdc++.h> #define ll long long #define pi pair <int,int> #define fi first #define se second using namespace std; const int N = 405, M = 1005, INF = (1<<30), MAX_IT = 140000000; int n, m, k; vector <pi> E(M); vector < vector <int> > In(N+1), Out(N+1); vector <int> Forward(N+2), Backward(N+2), A(N+1), Pos; ll power(ll n, ll k) { return (k == 0) ? 1 : n * pow(n, k-1); } void count_forward_and_backward(int n, vector <bool> &Del) { for (int i = 1; i <= n; i++) Forward[i] = Backward[i] = 0; for (int u = 1; u <= n; u++) for (int p : In[u]) if (!Del[p] && !Del[u]) Backward[u] = max(Backward[u], Backward[p]+1); for (int u = n; u >= 1; u--) for (int v : Out[u]) if (!Del[v] && !Del[u]) Forward[u] = max(Forward[u], Forward[v]+1); } int get_answer_for_deleted(int n, int k, vector <bool> &Del) { count_forward_and_backward(n, Del); int ans = 0; for (int u = 1; u <= n; u++) if (!Del[u]) ans = max(ans, Backward[u] + Forward[u] + 1); return ans; } int check_all_combinations(int i, int n, int d, int k, vector <int> &A, vector <bool> &Del) { if (d == k) return get_answer_for_deleted(n, k, Del); if (i+(k-d-1) > n) return INF; int ans = INF; for (int j = i; j <= n; j++) { Del[A[j]] = true; ans = min(ans, check_all_combinations(j+1, n, d+1, k, A, Del)); Del[A[j]] = false; } return ans; } void get_rands(int n, int k, vector <int> &R) { for (int i = 0; i < k; i++) R[i] = abs(rand()) % n; } int solve(int n, int k) { vector <bool> Del(n+1, false); if (k <= 1 || power(n, k) * (n+m) <= MAX_IT) { for (int i = 1; i <= n; i++) A[i] = i; return check_all_combinations(1, n, 0, k, A, Del); } else { int ans = get_answer_for_deleted(n, k, Del), cur; vector <int> Rands(k); int siz = 0, siz1 = 0; vector <int> Pos, New; for (int u = 1; u <= n; u++) { //cout << u << " " << Forward[u] << " " << Backward[u] <<endl; if (2 * min(Forward[u], Backward[u])+1 >= ans-1) { Pos.push_back(u); siz++; New.push_back(u); siz1++; } } //cout << ans << " " << siz << " " << siz1 <<endl; int from_new, r, mod = min(k+1, siz1+1); for (int it = 0; (n+m) * it < MAX_IT; it++) { get_rands(siz, k, Rands); if (siz1 > 0) { from_new = abs(rand()) % mod; //cout << from_new << " " << siz1 <<endl; map <int,int> M; for (int i = 0; i < from_new; i++) { r = siz - siz1 + abs(rand()) % siz1; if (M[r] == 0) Rands[i] = r, M[r] = 1; } } for (int v : Rands) Del[Pos[v]] = true; cur = get_answer_for_deleted(n, k, Del); for (int v : Rands) Del[Pos[v]] = false; if (cur < ans) { if (ans - cur > 1 || (ans - cur == 1 && (cur - 1 + 2) % 2 == 1)) { New.clear(); siz1 = 0; count_forward_and_backward(n, Del); for (int u = 1; u <= n; u++) { if ((Forward[u] + Backward[u]) != 0 && 2 * min(Forward[u], Backward[u])+1 >= cur-1 && 2 * min(Forward[u], Backward[u])+1 < ans-1) { Pos.push_back(u); siz++; New.push_back(u); siz1++; } } } mod = min(k+1, siz1+1); //cout << "NEW " << cur << " " << ans << " " << siz << " " << siz1 <<endl; ans = cur; } } //cout << ans << " " << siz << " " << siz1 <<endl; for (int it = 0; it < 1000; it++) { get_rands(n, k, Rands); for (int v : Rands) Del[v] = true; ans = min(ans, get_answer_for_deleted(n, k, Del)); for (int v : Rands) Del[v] = false; } return ans; } } int main() { srand(time(NULL)); ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0); cin >> n >> m >> k; for (int i = 0; i < m; i++) { cin >> E[i].fi >> E[i].se; In[E[i].se].push_back(E[i].fi); Out[E[i].fi].push_back(E[i].se); } cout << solve(n, k) <<endl; /*cout << 300 << " " << 299 << " " << 3 <<endl; for (int i = 1; i+1 <= 300; i++) cout << i << " " << i+1 <<endl;*/ 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 | #include <bits/stdc++.h> #define ll long long #define pi pair <int,int> #define fi first #define se second using namespace std; const int N = 405, M = 1005, INF = (1<<30), MAX_IT = 140000000; int n, m, k; vector <pi> E(M); vector < vector <int> > In(N+1), Out(N+1); vector <int> Forward(N+2), Backward(N+2), A(N+1), Pos; ll power(ll n, ll k) { return (k == 0) ? 1 : n * pow(n, k-1); } void count_forward_and_backward(int n, vector <bool> &Del) { for (int i = 1; i <= n; i++) Forward[i] = Backward[i] = 0; for (int u = 1; u <= n; u++) for (int p : In[u]) if (!Del[p] && !Del[u]) Backward[u] = max(Backward[u], Backward[p]+1); for (int u = n; u >= 1; u--) for (int v : Out[u]) if (!Del[v] && !Del[u]) Forward[u] = max(Forward[u], Forward[v]+1); } int get_answer_for_deleted(int n, int k, vector <bool> &Del) { count_forward_and_backward(n, Del); int ans = 0; for (int u = 1; u <= n; u++) if (!Del[u]) ans = max(ans, Backward[u] + Forward[u] + 1); return ans; } int check_all_combinations(int i, int n, int d, int k, vector <int> &A, vector <bool> &Del) { if (d == k) return get_answer_for_deleted(n, k, Del); if (i+(k-d-1) > n) return INF; int ans = INF; for (int j = i; j <= n; j++) { Del[A[j]] = true; ans = min(ans, check_all_combinations(j+1, n, d+1, k, A, Del)); Del[A[j]] = false; } return ans; } void get_rands(int n, int k, vector <int> &R) { for (int i = 0; i < k; i++) R[i] = abs(rand()) % n; } int solve(int n, int k) { vector <bool> Del(n+1, false); if (k <= 1 || power(n, k) * (n+m) <= MAX_IT) { for (int i = 1; i <= n; i++) A[i] = i; return check_all_combinations(1, n, 0, k, A, Del); } else { int ans = get_answer_for_deleted(n, k, Del), cur; vector <int> Rands(k); int siz = 0, siz1 = 0; vector <int> Pos, New; for (int u = 1; u <= n; u++) { //cout << u << " " << Forward[u] << " " << Backward[u] <<endl; if (2 * min(Forward[u], Backward[u])+1 >= ans-1) { Pos.push_back(u); siz++; New.push_back(u); siz1++; } } //cout << ans << " " << siz << " " << siz1 <<endl; int from_new, r, mod = min(k+1, siz1+1); for (int it = 0; (n+m) * it < MAX_IT; it++) { get_rands(siz, k, Rands); if (siz1 > 0) { from_new = abs(rand()) % mod; //cout << from_new << " " << siz1 <<endl; map <int,int> M; for (int i = 0; i < from_new; i++) { r = siz - siz1 + abs(rand()) % siz1; if (M[r] == 0) Rands[i] = r, M[r] = 1; } } for (int v : Rands) Del[Pos[v]] = true; cur = get_answer_for_deleted(n, k, Del); for (int v : Rands) Del[Pos[v]] = false; if (cur < ans) { if (ans - cur > 1 || (ans - cur == 1 && (cur - 1 + 2) % 2 == 1)) { New.clear(); siz1 = 0; count_forward_and_backward(n, Del); for (int u = 1; u <= n; u++) { if ((Forward[u] + Backward[u]) != 0 && 2 * min(Forward[u], Backward[u])+1 >= cur-1 && 2 * min(Forward[u], Backward[u])+1 < ans-1) { Pos.push_back(u); siz++; New.push_back(u); siz1++; } } } mod = min(k+1, siz1+1); //cout << "NEW " << cur << " " << ans << " " << siz << " " << siz1 <<endl; ans = cur; } } //cout << ans << " " << siz << " " << siz1 <<endl; for (int it = 0; it < 1000; it++) { get_rands(n, k, Rands); for (int v : Rands) Del[v] = true; ans = min(ans, get_answer_for_deleted(n, k, Del)); for (int v : Rands) Del[v] = false; } return ans; } } int main() { srand(time(NULL)); ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0); cin >> n >> m >> k; for (int i = 0; i < m; i++) { cin >> E[i].fi >> E[i].se; In[E[i].se].push_back(E[i].fi); Out[E[i].fi].push_back(E[i].se); } cout << solve(n, k) <<endl; /*cout << 300 << " " << 299 << " " << 3 <<endl; for (int i = 1; i+1 <= 300; i++) cout << i << " " << i+1 <<endl;*/ return 0; } |