#include <bits/stdc++.h>
//#define int long long
#define fi first
#define se second
#define pb push_back
#define faster ios_base::sync_with_stdio(0); cin.tie(0);
using namespace std;
using ll = long long;
using ull = unsigned ll;
using ld = long double;
using pii = pair <int, int>;
using pil = pair <int, ll>;
using pli = pair <ll, int>;
using pll = pair <ll, ll>;
mt19937 Rand(chrono::steady_clock::now().time_since_epoch().count());
ll min(const ll &a, const ll &b){
return (a < b) ? a : b;
}
ll max(const ll &a, const ll &b){
return (a > b) ? a : b;
}
//const ll Mod = 1000000007;
//const ll Mod2 = 999999999989;
//only use when required
const int maxN = 1e5 + 1;
int n, m, k;
struct TDSU{
vector <pii> save;
vector <int> lab;
TDSU(){}
TDSU(int _n){
lab.resize(_n, -1);
}
inline void resize(int _n){
lab.resize(_n, -1);
}
inline int find_set(int u){
if (lab[u] < 0) return u;
return lab[u] = find_set(lab[u]);
}
inline int find(int u){
if (lab[u] < 0) return u;
return find(lab[u]);
}
inline void merge(int u, int v){
if (lab[u] > lab[v]) swap(u, v);
save.pb({v, lab[v]});
lab[u] += lab[v];
lab[v] = u;
}
inline void undo(){
int v = save.back().fi;
int u = lab[v];
lab[v] = save.back().se;
lab[u] -= lab[v];
save.pop_back();
}
inline void clear(){
lab.clear();
save.clear();
}
inline void reset(int _n){
clear();
resize(_n);
}
inline void roll_back(int _n){
while (save.size() > _n) undo();
}
};
TDSU dsu;
int timedfs, low[maxN], num[maxN];
int id[maxN];
int mark[maxN];
int node_cnt;
struct TEdge{
int u, v, idx;
};
TEdge e[maxN];
vector <TEdge> adj[maxN];
void dfs(int u, int p){
low[u] = num[u] = ++timedfs;
for (auto i: adj[u]){
int v = i.u ^ i.v ^ u;
if (v == p) continue;
if (!num[v]){
dfs(v, u);
low[u] = min(low[u], low[v]);
if (low[v] == num[v]) mark[i.idx] = 1;
}
else{
low[u] = min(low[u], num[v]);
}
}
}
vector <pii> adj1[maxN];
int lift[20][maxN];
int depth[maxN];
int val[maxN];
void dfs1(int u, int p){
lift[u][0] = p;
depth[u] = depth[p] + 1;
for (int i = 1; i < 20; ++i){
lift[u][i] = lift[lift[u][i - 1]][i - 1];
if (!lift[u][i]) break;
}
for (auto i: adj1[u]){
int v = i.fi;
if (v == p) continue;
dfs1(v, u);
}
}
int lca(int u, int v){
if (depth[u] < depth[v]) swap(u, v);
int k = depth[u] - depth[v];
while (k){
int t = k & -k;
u = lift[u][__lg(t)];
k -= t;
}
if (u == v) return u;
for (int i = 19; i >= 0; --i){
if (lift[u][i] != lift[v][i]){
u = lift[u][i];
v = lift[v][i];
}
}
return lift[u][0];
}
void dfs2(int u, int p){
for (auto i: adj1[u]){
int v = i.fi;
if (v == p) continue;
dfs2(v, u);
val[u] += val[v];
if (!val[v]){
mark[abs(i.se)] = 0;
}
else if (val[v] * i.se < 0) mark[abs(i.se)] = 1;
else mark[abs(i.se)] = -1;
}
}
void Init(){
cin >> n >> m;
for (int i = 1; i <= m; ++i){
cin >> e[i].u >> e[i].v;
e[i].idx = i;
adj[e[i].u].pb(e[i]);
adj[e[i].v].pb(e[i]);
}
for (int i = 1; i <= n; ++i){
if (!num[i]) dfs(i, 0);
}
dsu.resize(n + 1);
vector <int> bridge;
for (int i = 1; i <= m; ++i){
if (!mark[i]){
int x = dsu.find_set(e[i].u);
int y = dsu.find_set(e[i].v);
if (x != y){
dsu.merge(x, y);
}
}
else bridge.pb(i);
}
for (int i = 1; i <= n; ++i){
int j = dsu.find_set(i);
if (!id[j]) id[j] = ++node_cnt;
id[i] = id[j];
}
for (int i: bridge){
int u = id[e[i].u];
int v = id[e[i].v];
adj1[u].pb({v, i});
adj1[v].pb({u, -i});
}
for (int i = 1; i <= node_cnt; ++i){
if (!lift[i][0]){
dfs1(i, 0);
}
}
cin >> k;
for (int i = 1; i <= k; ++i){
int u, v;
cin >> u >> v;
u = id[u];
v = id[v];
++val[u];
--val[v];
}
for (int i = 1; i <= node_cnt; ++i){
if (!lift[i][0]){
dfs2(i, 0);
}
}
for (int i = 1; i <= m; ++i){
if (!mark[i]) cout << 'B';
else if (mark[i] < 0) cout << 'L';
else cout << 'R';
}
}
#define debu
#define taskname "test"
signed main(){
if (fopen(taskname".inp", "r")){
freopen(taskname".inp", "r", stdin);
#ifdef debug
freopen(taskname".out", "w", stdout);
#endif
}
faster;
ll tt = 1;
//cin >> tt;
while (tt--){
Init();
}
if (fopen("timeout.txt", "r")){
ofstream timeout("timeout.txt");
timeout << 1000 * double(clock()) / CLOCKS_PER_SEC;
#ifndef debug
cerr << "\nTime elapsed: " << 1000 * double(clock()) / CLOCKS_PER_SEC << "ms\n";
#endif
}
}
Compilation message
oneway.cpp: In member function 'void TDSU::roll_back(int)':
oneway.cpp:72:28: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
72 | while (save.size() > _n) undo();
| ~~~~~~~~~~~~^~~~
oneway.cpp: In function 'int main()':
oneway.cpp:218:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
218 | freopen(taskname".inp", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 2 |
Incorrect |
4 ms |
5040 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 2 |
Incorrect |
4 ms |
5040 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 2 |
Incorrect |
4 ms |
5040 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
