Submission #526154

#TimeUsernameProblemLanguageResultExecution timeMemory
526154mjhmjh1104Mountains and Valleys (CCO20_day1problem3)C++17
0 / 25
7096 ms184004 KiB
#pragma GCC optimize("O3") #pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") #include <set> #include <tuple> #include <cstdio> #include <vector> #include <utility> #include <iterator> #include <algorithm> #include <functional> using namespace std; struct Item { int posde; int negde; int ans; Item (): posde((int)-1e9), negde((int)-1e9), ans((int)-1e9) {} Item (int posde, int negde, int ans): posde(posde), negde(negde), ans(ans) {} } sp_split[19][500006]; int n, m; vector<int> tree[500006], child[500006]; vector<tuple<int, int, int>> adj; int depth[500006], sp[19][500006], sp_dist[19][500006]; set<int, greater<int>> lt_depth[500006], lt_dist[500006]; int max_depth[500006], rev_max_depth[500006], dist[500006], rev_dist[500006]; int prev_dist[500006], prev_depth[500006][2]; inline Item query_sp_res(int A, int x) { if (A == -1) return Item(); Item ret = { prev_depth[x][0] + depth[x], prev_depth[x][0] - depth[x], (int)-1e9 }; if (A == x) return ret; for (int t = 18; t >= 0; t--) if (sp[t][x] != -1 && depth[sp[t][x]] > depth[A]) { ret.ans = max({ sp_split[t][x].ans, ret.ans, sp_split[t][x].posde + ret.negde }); ret.posde = max(sp_split[t][x].posde, ret.posde); ret.negde = max(sp_split[t][x].negde, ret.negde); x = sp[t][x]; } ret.ans = max({ sp_split[0][x].ans, ret.ans, sp_split[0][x].posde + ret.negde }); ret.posde = max(sp_split[0][x].posde, ret.posde); ret.negde = max(sp_split[0][x].negde, ret.negde); return ret; } int dfs_dist(int x) { max_depth[x] = 0; dist[x] = 0; int mx0 = (int)-1e9, mx1 = (int)-1e9; for (auto &i: child[x]) { int t = dfs_dist(i) + 1; max_depth[x] = max(max_depth[x], t); if (t > mx0) mx1 = mx0, mx0 = t; else if (t > mx1) mx1 = t; dist[x] = max(dist[x], dist[i]); } dist[x] = max(dist[x], mx0 + max(mx1, 0)); return max_depth[x]; } void dfs_rev_dist(int x) { lt_depth[x].insert(rev_max_depth[x]); lt_dist[x].insert(rev_dist[x]); for (auto &i: child[x]) { lt_depth[x].insert(max_depth[i] + 1); if (prev_depth[x][0] < max_depth[i] + 1) prev_depth[x][1] = prev_depth[x][0], prev_depth[x][0] = max_depth[i] + 1; else if (prev_depth[x][1] < max_depth[i] + 1) prev_depth[x][1] = max_depth[i] + 1; lt_dist[x].insert(dist[i]); if (prev_dist[x] < dist[i]) prev_dist[x] = dist[i]; } for (auto &i: child[x]) { lt_depth[x].erase(lt_depth[x].find(max_depth[i] + 1)); lt_dist[x].erase(lt_dist[x].find(dist[i])); if (!lt_dist[x].empty()) rev_dist[i] = *lt_dist[x].begin(); if (!lt_depth[x].empty()) rev_dist[i] = max(rev_dist[i], rev_max_depth[i] = *lt_depth[x].begin() + 1); if ((int)lt_depth[x].size() > 1) rev_dist[i] = max(rev_dist[i], *lt_depth[x].begin() + *prev(prev(lt_depth[x].end()))); lt_depth[x].insert(max_depth[i] + 1); lt_dist[x].insert(dist[i]); } lt_depth[x].erase(lt_depth[x].find(rev_max_depth[x])); lt_dist[x].erase(lt_dist[x].find(rev_dist[x])); for (auto &i: child[x]) dfs_rev_dist(i); } void dfs_f_dist(int x) { for (auto &i: child[x]) { lt_dist[x].erase(lt_dist[x].find(dist[i])); sp_dist[0][i] = (lt_dist[x].empty() ? 0 : *lt_dist[x].begin()); lt_dist[x].insert(dist[i]); } for (auto &i: child[x]) dfs_f_dist(i); } void dfs_edge(int x) { for (auto &i: child[x]) { lt_depth[x].erase(lt_depth[x].find(max_depth[i] + 1)); if ((int)lt_depth[x].size() > 1) sp_dist[0][i] = max(sp_dist[0][i], *lt_depth[x].begin() + *prev(prev(lt_depth[x].end()))); else if (!lt_depth[x].empty()) sp_dist[0][i] = max(sp_dist[0][i], *lt_depth[x].begin()); int V = (lt_depth[x].empty() ? 0 : *lt_depth[x].begin()); sp_split[0][i].posde = V + depth[x]; sp_split[0][i].negde = V - depth[x]; lt_depth[x].insert(max_depth[i] + 1); } for (auto &i: child[x]) dfs_edge(i); } void dfs_child(int x, int prev = -1) { sp[0][x] = prev; for (auto &i: tree[x]) if (i != prev) { depth[i] = depth[x] + 1; child[x].push_back(i); dfs_child(i, x); } } int A, B; inline int lca(int u, int v) { bool sw = false; if (depth[u] < depth[v]) swap(u, v), sw = true; int diff = depth[u] - depth[v] - 1; if (~diff) { for (int t = 18; t >= 0; t--) if (diff >= 1 << t) { diff -= 1 << t; u = sp[t][u]; } if (sw) B = u; else A = u; u = sp[0][u]; if (u == v) return u; } for (int t = 18; t >= 0; t--) if (sp[t][u] != -1 && sp[t][v] != -1 && sp[t][u] != sp[t][v]) { u = sp[t][u]; v = sp[t][v]; } A = u, B = v; if (sw) swap(A, B); return sp[0][u]; } inline int query_sp_dist(int u, int v, int l, int A, int B, int G, int H) { int ret = 0; if (u != l) { ret = max(prev_depth[u][0] + prev_depth[u][1], prev_dist[u]); u = sp[0][u]; } if (v != l) { ret = max(prev_depth[v][0] + prev_depth[v][1], prev_dist[v]); v = sp[0][v]; } for (int t = 18; t >= 0; t--) if (sp[t][u] != -1 && depth[sp[t][u]] > depth[l]) { ret = max(ret, sp_dist[t][u]); u = sp[t][u]; } for (int t = 18; t >= 0; t--) if (sp[t][v] != -1 && depth[sp[t][v]] > depth[l]) { ret = max(ret, sp_dist[t][v]); v = sp[t][v]; } if (A != -1) lt_dist[l].erase(lt_dist[l].find(dist[A])); if (B != -1) lt_dist[l].erase(lt_dist[l].find(dist[B])); ret = max(ret, lt_dist[l].empty() ? 0 : *lt_dist[l].begin()); if (A != -1) lt_dist[l].insert(dist[A]); if (B != -1) lt_dist[l].insert(dist[B]); return ret; } int main() { scanf("%d%d", &n, &m); while (m--) { int x, y, w; scanf("%d%d%d", &x, &y, &w); if (w == 1) { tree[x].push_back(y); tree[y].push_back(x); } else adj.push_back({ x, y, w }); } for (int i = 0; i < n; i++) prev_dist[i] = prev_depth[i][0] = prev_depth[i][1] = (int)-1e9; dfs_child(0); dfs_dist(0); dfs_rev_dist(0); dfs_f_dist(0); dfs_edge(0); for (int t = 1; t < 19; t++) for (int i = 0; i < n; i++) { if (sp[t - 1][i] == -1) { sp[t][i] = -1; sp_dist[t][i] = sp_dist[t - 1][i]; sp_split[t][i] = sp_split[t - 1][i]; } else { sp[t][i] = sp[t - 1][sp[t - 1][i]]; sp_dist[t][i] = max(sp_dist[t - 1][i], sp_dist[t - 1][sp[t - 1][i]]); sp_split[t][i].ans = max({ sp_split[t - 1][sp[t - 1][i]].ans, sp_split[t - 1][i].ans, sp_split[t - 1][sp[t - 1][i]].posde + sp_split[t - 1][i].negde }); sp_split[t][i].posde = max(sp_split[t - 1][sp[t - 1][i]].posde, sp_split[t - 1][i].posde); sp_split[t][i].negde = max(sp_split[t - 1][sp[t - 1][i]].negde, sp_split[t - 1][i].negde); } } int res = 2 * (n - 1) - dist[0]; for (auto [ i, j, w ]: adj) { A = B = -1; int l = lca(i, j); int ds = depth[i] + depth[j] - depth[l] - depth[l]; int curr = w + 2 * (n - 1) - ds - 1; int G = 0, H = 0, y = 0; if (A != -1) lt_depth[l].erase(lt_depth[l].find(max_depth[A] + 1)); if (B != -1) lt_depth[l].erase(lt_depth[l].find(max_depth[B] + 1)); if (!lt_depth[l].empty()) G = *lt_depth[l].begin(); y = max(y, G + rev_max_depth[l] - 1); if ((int)lt_depth[l].size() > 1) y = max(y, G + *next(lt_depth[l].begin()) - 1); if (A != -1) lt_depth[l].insert(max_depth[A] + 1); if (B != -1) lt_depth[l].insert(max_depth[B] + 1); Item first = query_sp_res(A, i); Item second = query_sp_res(B, j); int Alt = first.negde + depth[l]; int Brt = second.negde + depth[l]; int Lt = max(rev_max_depth[l], G); res = min(res, curr - max({ y, Alt + max(Brt, Lt) + 1, max(Alt, Lt) + Brt + 1, first.ans + 1, second.ans + 1, rev_dist[l] - 1, query_sp_dist(i, j, l, A, B, G, H) - 1 })); } printf("%d", res); }

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:170:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  170 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~
Main.cpp:173:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  173 |         scanf("%d%d%d", &x, &y, &w);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~
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