#include<bits/stdc++.h>
using namespace std;
#define dbg(a) cerr << #a << ": " << a << "\n"
using ll = long long;
struct graph {
int n, t, sz;
vector<vector<int>> adj;
vector<int> tin, low, cmp;
graph(int n): n(n),adj(n),tin(n),low(n),cmp(n){}
void add_edge(int u, int v){
adj[u].push_back(v);
adj[v].push_back(u);
}
void dfs(int u, int p){
tin[u]=low[u]=t++;
int cnt=0;
for(int v: adj[u]){
if(v==p and ++cnt <= 1) continue;
if(tin[v]!=-1) low[u] = min(low[u], tin[v]);
else {
dfs(v,u);
low[u] = min(low[u], low[v]);
}
}
}
void dfs2(int u, int p){
if(p!=-1 and tin[p]>=low[u]) cmp[u] = cmp[p];
else cmp[u] = sz++;
for(int v: adj[u]){
if(cmp[v]==-1) dfs2(v,u);
}
}
void process_2ecc(){
t = 0, sz = 0;
for (int i = 0; i < n; ++i){
tin[i] = low[i] = cmp[i] = -1;
}
for (int i = 0; i < n; ++i){
if(tin[i]==-1) dfs(i,-1);
}
for (int i = 0; i < n; ++i){
if(cmp[i]==-1) dfs2(i,-1);
}
}
};
const int N = 1e5+5, LG = 20;
int par[N][LG];
vector<array<int, 3>> adj[N];
vector<int> dep(N), tin(N, -1), tout(N), mn_left(N, N), mn_right(N, N);
char ans[N];
int t = 0;
void dfs(int u, int p) {
tin[u] = t++;
for (int k = 1; k < LG; ++k) {
par[u][k] = par[par[u][k - 1]][k - 1];
}
for (auto [v, e, dir]: adj[u]) {
if (v != p) {
dep[v] = dep[u] + 1;
par[v][0] = u;
dfs(v, u);
}
}
tout[u] = t++;
}
bool is_anc(int u, int v) {
return (tin[u] <= tin[v] and tout[v] <= tout[u]);
}
int get_lca(int u, int v) {
if (is_anc(u, v)) return u;
if (is_anc(v, u)) return v;
for (int j = LG - 1; j >= 0; --j) {
if (!is_anc(par[u][j], v)) {
u = par[u][j];
}
}
return par[u][0];
}
vector<int> vis(N);
void dfs2(int u, int p) {
vis[u] = 1;
for (auto [v, e, dir]: adj[u]) {
if (!vis[v]) {
dfs2(v, u);
if (mn_left[v] <= dep[u]) { // v -> u
if (dir == 0) { //
ans[e] = 'L';
}
else {
ans[e] = 'R';
}
}
if (mn_right[v] <= dep[u]) { // u -> v
if (dir == 0) {
ans[e] = 'R';
}
else {
ans[e] = 'L';
}
}
mn_left[u] = min(mn_left[u], mn_left[v]);
mn_right[u] = min(mn_right[u], mn_right[v]);
}
}
}
void solve() {
int n, m; cin >> n >> m;
graph g(n);
vector<array<int, 2>> edges(m);
for (auto &[u, v]: edges) {
cin >> u >> v; u--, v--;
if (u != v) {
g.add_edge(u, v);
}
}
g.process_2ecc();
for (int e = 0; e < m; ++e) {
ans[e] = 'B';
auto [u, v] = edges[e];
u = g.cmp[u];
v = g.cmp[v];
if (u != v) {
adj[u].push_back({v, e, 0});
adj[v].push_back({u, e, 1});
}
}
for (int u = 0; u < n; ++u) {
if (tin[u] == -1) {
par[u][0] = u;
dfs(u, -1);
}
}
int q; cin >> q;
while (q--) {
int u, v; cin >> u >> v; u--, v--;
u = g.cmp[u];
v = g.cmp[v];
int l = get_lca(u, v);
mn_left[u] = min(mn_left[u], dep[l]);
mn_right[v] = min(mn_right[v], dep[l]);
}
for (int u = 0; u < n; ++u) {
if (!vis[u]) {
dfs2(u, u);
}
}
cout << ans << "\n";
}
int main(){
ios::sync_with_stdio(0), cin.tie(0);
int tc = 1;
for (int t = 1; t <= tc; ++t) {
solve();
}
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
3 ms |
4948 KB |
Output is correct |
2 |
Correct |
4 ms |
4948 KB |
Output is correct |
3 |
Correct |
3 ms |
5056 KB |
Output is correct |
4 |
Correct |
4 ms |
5168 KB |
Output is correct |
5 |
Correct |
3 ms |
5204 KB |
Output is correct |
6 |
Correct |
3 ms |
5076 KB |
Output is correct |
7 |
Correct |
3 ms |
5204 KB |
Output is correct |
8 |
Correct |
4 ms |
5204 KB |
Output is correct |
9 |
Correct |
3 ms |
5056 KB |
Output is correct |
10 |
Correct |
4 ms |
5076 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
3 ms |
4948 KB |
Output is correct |
2 |
Correct |
4 ms |
4948 KB |
Output is correct |
3 |
Correct |
3 ms |
5056 KB |
Output is correct |
4 |
Correct |
4 ms |
5168 KB |
Output is correct |
5 |
Correct |
3 ms |
5204 KB |
Output is correct |
6 |
Correct |
3 ms |
5076 KB |
Output is correct |
7 |
Correct |
3 ms |
5204 KB |
Output is correct |
8 |
Correct |
4 ms |
5204 KB |
Output is correct |
9 |
Correct |
3 ms |
5056 KB |
Output is correct |
10 |
Correct |
4 ms |
5076 KB |
Output is correct |
11 |
Correct |
41 ms |
11256 KB |
Output is correct |
12 |
Correct |
43 ms |
13152 KB |
Output is correct |
13 |
Correct |
51 ms |
16076 KB |
Output is correct |
14 |
Correct |
66 ms |
20680 KB |
Output is correct |
15 |
Correct |
75 ms |
22232 KB |
Output is correct |
16 |
Correct |
94 ms |
25884 KB |
Output is correct |
17 |
Correct |
87 ms |
27252 KB |
Output is correct |
18 |
Correct |
90 ms |
25876 KB |
Output is correct |
19 |
Correct |
86 ms |
28400 KB |
Output is correct |
20 |
Correct |
46 ms |
15308 KB |
Output is correct |
21 |
Correct |
44 ms |
15120 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
3 ms |
4948 KB |
Output is correct |
2 |
Correct |
4 ms |
4948 KB |
Output is correct |
3 |
Correct |
3 ms |
5056 KB |
Output is correct |
4 |
Correct |
4 ms |
5168 KB |
Output is correct |
5 |
Correct |
3 ms |
5204 KB |
Output is correct |
6 |
Correct |
3 ms |
5076 KB |
Output is correct |
7 |
Correct |
3 ms |
5204 KB |
Output is correct |
8 |
Correct |
4 ms |
5204 KB |
Output is correct |
9 |
Correct |
3 ms |
5056 KB |
Output is correct |
10 |
Correct |
4 ms |
5076 KB |
Output is correct |
11 |
Correct |
41 ms |
11256 KB |
Output is correct |
12 |
Correct |
43 ms |
13152 KB |
Output is correct |
13 |
Correct |
51 ms |
16076 KB |
Output is correct |
14 |
Correct |
66 ms |
20680 KB |
Output is correct |
15 |
Correct |
75 ms |
22232 KB |
Output is correct |
16 |
Correct |
94 ms |
25884 KB |
Output is correct |
17 |
Correct |
87 ms |
27252 KB |
Output is correct |
18 |
Correct |
90 ms |
25876 KB |
Output is correct |
19 |
Correct |
86 ms |
28400 KB |
Output is correct |
20 |
Correct |
46 ms |
15308 KB |
Output is correct |
21 |
Correct |
44 ms |
15120 KB |
Output is correct |
22 |
Correct |
135 ms |
28488 KB |
Output is correct |
23 |
Correct |
131 ms |
26856 KB |
Output is correct |
24 |
Correct |
130 ms |
27040 KB |
Output is correct |
25 |
Correct |
124 ms |
31428 KB |
Output is correct |
26 |
Correct |
141 ms |
28012 KB |
Output is correct |
27 |
Correct |
137 ms |
27032 KB |
Output is correct |
28 |
Correct |
28 ms |
8204 KB |
Output is correct |
29 |
Correct |
64 ms |
16204 KB |
Output is correct |
30 |
Correct |
65 ms |
16340 KB |
Output is correct |
31 |
Correct |
64 ms |
16416 KB |
Output is correct |
32 |
Correct |
85 ms |
20524 KB |
Output is correct |