Submission #1010843

#TimeUsernameProblemLanguageResultExecution timeMemory
1010843voiOne-Way Streets (CEOI17_oneway)C++17
0 / 100
3050 ms10844 KiB
#include <bits/stdc++.h> #define all(s) s.begin(), s.end() #define lb(s, a) lower_bound(all(s), (a)) - s.begin() #define ii pair <int, int> #define fi first #define se second using namespace std; typedef long long ll; const int ar = 2e5+2; const ll mod = 1e9+7; const int oo = 1e9; int n, m; int timeDfs = 0, scc = 0; int low[ar], num[ar]; int id[ar]; bool deleted[ar]; vector <int> tplt[ar]; struct set3 { int v, i, t; }; vector <set3> g[ar]; stack <int> st; void dfs(int u, int p) { num[u] = low[u] = ++timeDfs; st.push(u); for (auto [v, i, t] : g[u]) if(v != p) { if (deleted[v]) continue; if (!num[v]){ dfs(v, u); low[u] = min(low[u], low[v]); } else low[u] = min(low[u], num[v]); } if (low[u] == num[u]) { scc++; int v; do { v = st.top(); st.pop(); tplt[scc].push_back(v); id[v] = scc; deleted[v] = true; } while (v != u); } } int h[ar], up[ar][18], val[ar]; set3 par[ar]; void dfs2(int u, int p) { for(auto x : tplt[u]) { for(auto [v, i, t] : g[x]) { v = id[v]; if(v == u || v == p) continue; h[v] = h[u] + 1; up[v][0] = u; par[v] = {u, i, t}; for(int j = 1; j < 17; ++j) up[v][j] = up[up[v][j - 1]][j - 1]; dfs2(v, u); } } } int lca(int u, int v) { if(h[u] != h[v]) { if(h[u] < h[v]) swap(u, v); int k = h[u] - h[v]; for(int j = 0; (1 << j) <= k; ++j) if(k >> j & 1) u = up[u][j]; } if(u == v) return u; int k = 31 - __builtin_clz(h[u]); for(int j = k; j >= 0; --j) if(up[u][j] != up[v][j]) { u = up[u][j]; v = up[v][j]; } return up[u][0]; } void direct(int u, int p, int t) { int goc = u; if(u == p) return; while(u != p) { if(h[par[u].v] < h[p]) break; val[par[u].i] = par[u].t ^ t; u = par[u].v; } u = goc; set3 tmp; while(u != p) { if(h[par[u].v] < h[p]) break; tmp = par[u]; par[u] = tmp; u = tmp.v; } } signed main() { ios_base::sync_with_stdio(0); cin.tie(0), cout.tie(0); #define task "CEOI17_ONEWAY" if(fopen(task".inp", "r")) { freopen(task".inp", "r", stdin); freopen(task".out", "w", stdout); } cin >> n >> m; int u, v; memset(val, -1, sizeof val); for(int i = 1; i <= m; ++i) { cin >> u >> v; g[u].push_back({v, i, 0}); g[v].push_back({u, i, 1}); } for(int i = 1; i <= n; ++i) if(id[i] == 0) { dfs(i, 0); dfs2(id[i], 0); } int q; cin >> q; while(q--) { cin >> u >> v; u = id[u]; v = id[v]; int p = lca(u, v); direct(u, p, 0); direct(v, p, 1); } for(int i = 1; i <= m; ++i) if(val[i] == -1) cout << 'B'; else if(val[i] == 0) cout << 'L'; else cout << 'R'; }

Compilation message (stderr)

oneway.cpp: In function 'int main()':
oneway.cpp:114:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  114 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:115:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  115 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
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