Submission #1005491

#TimeUsernameProblemLanguageResultExecution timeMemory
1005491serifefedartarOne-Way Streets (CEOI17_oneway)C++17
0 / 100
1 ms10584 KiB
#include <bits/stdc++.h> using namespace std; #define fast ios::sync_with_stdio(0);cin.tie(0); typedef long long ll; #define f first #define s second #define LOGN 20 const ll MOD = 1e9 + 7; const ll MAXN = 1e5 + 100; vector<vector<int>> graph, G, G2; int mark[MAXN], a[MAXN], b[MAXN], vis[MAXN], par[MAXN], sz[MAXN], ways[MAXN]; int up[LOGN][MAXN], depth[MAXN]; void dfs(int node, int parent) { vis[node] = 1; for (auto u : graph[node]) { if (u != parent && vis[u] != 2) G[node].push_back(u); if (!vis[u]) dfs(u, node); } vis[node] = 2; } int find(int node) { if (node == par[node]) return node; return par[node] = find(par[node]); } void unite(int a, int b) { a = find(a); b = find(b); if (a == b) return ; if (sz[b] > sz[a]) swap(a, b); par[b] = a; sz[a] += sz[b]; } stack<int> nds; void dfs2(int node) { vis[node] = true; nds.push(node); for (auto u : G[node]) { if (vis[u] == 0) dfs2(u); } } void dfs3(int node) { vis[node] = true; for (auto u : G[node]) { if (vis[u]) continue; unite(node, u); dfs3(u); } } void prep(int node, int parent) { for (auto u : G2[node]) { if (u != parent) { up[0][u] = node; depth[u] = depth[node] + 1; for (int i = 1; i < LOGN; i++) up[i][u] = up[i-1][up[i-1][u]]; } } } int lift(int node, int k) { for (int i = 0; i < LOGN; i++) { if ((1<<i) & k) node = up[i][node]; } return node; } int lca(int a, int b) { if (depth[b] > depth[a]) swap(a, b); a = lift(a, depth[a] - depth[b]); if (a == b) return a; for (int i = LOGN-1; i >= 0; i--) { if (up[i][a] != up[i][b]) { a = up[i][a]; b = up[i][b]; } } return up[0][a]; } map<pair<int,int>,int> mp; int dfs4(int node, int parent) { for (auto u : G2[node]) { if (u == parent) continue; dfs4(u, node); mark[node] += mark[u]; if (mark[u]) { // edge : u -> node if (mp[{u, node}] == 0) ways[mp[{node, u}]] = 1; else ways[mp[{u, node}]] = 2; } else { // edge : node -> u if (mp[{u, node}] == 0) ways[mp[{node, u}]] = 2; else ways[mp[{u, node}]] = 1; } } return mark[node]; } int main() { fast int n, m, q; cin >> n >> m; for (int i = 1; i <= n; i++) par[i] = i, sz[i] = 1; graph = vector<vector<int>>(n+1, vector<int>()); G = vector<vector<int>>(n+1, vector<int>()); G2 = vector<vector<int>>(n+1, vector<int>()); for (int i = 1; i <= m; i++) { cin >> a[i] >> b[i]; graph[a[i]].push_back(b[i]); graph[b[i]].push_back(a[i]); } dfs(1, 1); for (int i = 1; i <= n; i++) vis[i] = 0; dfs2(1); for (int i = 1; i <= n; i++) vis[i] = 0; while (nds.size()) { int node = nds.top(); nds.pop(); if (!vis[node]) dfs3(node); } for (int i = 1; i <= m; i++) mp[{find(a[i]), find(b[i])}] = i; for (int i = 1; i <= m; i++) { if (find(a[i]) == find(b[i])) ways[i] = -1; else { G2[find(a[i])].push_back(find(b[i])); G2[find(b[i])].push_back(find(a[i])); } } for (int i = 0; i < LOGN; i++) up[i][find(1)] = 1; prep(find(1), find(1)); cin >> q; while (q--) { int a, b; cin >> a >> b; a = find(a); b = find(b); if (a == b) continue; mark[a] += 1; mark[lca(a, b)] += -1; } dfs4(find(1), find(1)); for (int i = 1; i <= m; i++) { if (ways[i] == -1) cout << "B"; else if (ways[i] == 1) cout << "L"; else if (ways[i] == 2) cout << "R"; else cout << "B"; } cout << "\n"; }
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