#include <bits/stdc++.h>
#define lli long long int
#define ld long double
#define pb push_back
#define MP make_pair
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define REP(i, n) for(int i = 0; (i) < (n); (i)++)
using namespace std;
void fastio() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
}
const int N = 1e5 + 5;
const int INF = 1e9 + 500;
const int LGN = 20;
int n, m;
vector<array<int, 2> > edg(N);
vector<char> res(N, '$');
struct Bridge {
vector<vector<array<int, 2> > > adj;
vector<int> tin, low;
vector<bool> isBr;
int tim = 0;
int curc = 0;
Bridge() {
tin.assign(N, -1);
low.assign(N, 0);
isBr.assign(N, 0);
adj.assign(N, vector<array<int, 2> >());
}
void dfs(int node, int pedg) {
tin[node] = low[node] = tim++;
for(auto c : adj[node]) {
if(c[1] == pedg) continue;
if(tin[c[0]] != -1) {
low[node] = min(low[node], tin[c[0]]);
}
else {
dfs(c[0], c[1]);
low[node] = min(low[node], low[c[0]]);
if(low[c[0]] > tin[node]) {
//bridge found
isBr[c[1]] = 1;
}
}
}
}
void dfs2(int node, vector<int> &comp) {
for(auto c : adj[node]) {
if(comp[c[0]] != -1) {
continue;
}
if(isBr[c[1]]) {
comp[c[0]] = curc++;
dfs2(c[0], comp);
}
else {
comp[c[0]] = comp[node];
dfs2(c[0], comp);
}
}
}
void find_comp(vector<int> &comp) {
curc = 0;
comp.assign(n + 1, -1);
for(int i = 1; i <= n; i++) {
if(comp[i] != -1) continue;
comp[i] = curc++;
dfs2(i, comp);
}
}
};
struct DifArr {
vector<int> st;
int n;
void reset(int nn) {
n = nn;
st.assign(n + 3, 0);
}
void update(int l, int r) {
st[l]++; st[r + 1]--;
}
void get_arr() {
for(int i = 1; i <= n; i++) {
st[i] += st[i - 1];
}
}
};
struct Tre {
vector<vector<array<int, 2> > > adj;
vector<int> head;
vector<int> subt, dep, tin;
vector<int> p, pedg;
int tim;
int n;
DifArr st1, st2;
Tre() {
adj.assign(N, vector<array<int, 2> >());
subt.assign(N, -1);
dep.assign(N, 0);
tin.assign(N, 0);
p.assign(N, 0);
head.assign(N, 0);
pedg.assign(N, 0);
}
void dfssz(int node) {
subt[node] = 1;
for(auto &c : adj[node]) {
p[c[0]] = node; pedg[c[0]] = c[1];
adj[c[0]].erase(find(all(adj[c[0]]), array<int,2>({node, c[1]})));
dfssz(c[0]);
subt[node] += subt[c[0]];
if(subt[adj[node][0][0]] < subt[c[0]]) {
swap(adj[node][0], c);
}
}
}
void dfshld(int node) {
tin[node] = tim++;
for(auto c : adj[node]) {
head[c[0]] = (c == adj[node][0]) ? head[node] : c[0];
dep[c[0]] = dep[node] + 1;
dfshld(c[0]);
}
}
int lca(int x, int y) {
while(head[x] != head[y]) {
if(dep[head[x]] < dep[head[y]]) swap(x, y);
x = p[head[x]];
}
if(dep[x] < dep[y]) {
swap(x, y);
}
return y;
}
void init(int curc) {
n = curc;
for(int i = 0; i < n; i++) {
if(subt[i] != -1) continue;
dep[i] = tim = 0; dfssz(i);
head[i] = i; dfshld(i);
}
st1.reset(n + 2);
st2.reset(n + 2);
}
void upd(int x, int lc, DifArr &st) { // dep[lc] < dep[x]
// DONT UPD LCA
while(head[x] != head[lc]) {
st.update(tin[head[x]], tin[x]);
x = p[head[x]];
}
if(lc == x) return;
st.update(tin[lc] + 1, tin[x]);
}
};
void solve() {
cin >> n >> m;
for(int i = 0; i < m; i++) {
cin >> edg[i][0] >> edg[i][1];
}
Bridge br;
for(int i = 0; i < m; i++) {
br.adj[edg[i][0]].pb({edg[i][1], i});
br.adj[edg[i][1]].pb({edg[i][0], i});
}
for(int i = 1; i<=n; i++) {
if(br.tin[i] != -1) continue;
br.dfs(i, m);
}
vector<int> cmp;
br.find_comp(cmp);
// for(int i = 0; i < m; i++) {
// if(br.isBr[i]) {
// cout << "i:" << i << " a:" << edg[i][0] << " b:" << edg[i][1] << "\n";
// }
// }
// for(int i = 1; i <= n; i++) {
// cout << cmp[i] << " ";
// }
// cout << endl;
Tre t;
for(int i = 0; i < m; i++) {
if(!br.isBr[i]) {
res[i] = 'B';
}
else {
edg[i] = {cmp[edg[i][0]], cmp[edg[i][1]]};
t.adj[edg[i][0]].pb({edg[i][1], i});
t.adj[edg[i][1]].pb({edg[i][0], i});
}
}
t.init(br.curc);
// for(int i = 0; i < br.curc; i++) {
// cout << "i:" << i <<" p:" << t.p[i] << endl;
// }
int p;
cin >> p;
REP(i, p) {
int x, y;
cin >> x >> y;
x = cmp[x]; y = cmp[y];
if(x == y) continue;
int lc = t.lca(x, y);
// cout << "x:" << x << " y:" << y << " lca:" << lc << "\n";
t.upd(x, lc, t.st1);
t.upd(y, lc, t.st2);
}
t.st1.get_arr();
t.st2.get_arr();
for(int i = 1; i < br.curc; i++) {
int cur = t.pedg[i];
// cout << "curc:" << i << " vals: ";
// cout << t.st1.st[t.tin[i]] << " " << t.st2.st[t.tin[i]] << endl;
assert(!(t.st1.st[t.tin[i]] > 0 && t.st2.st[t.tin[i]] > 0));
if(!t.st1.st[t.tin[i]] && !t.st2.st[t.tin[i]]) {
res[cur] = 'B';
}
else if(t.st1.st[t.tin[i]] && !t.st2.st[t.tin[i]]) {
if(edg[cur][0] == i) {
res[cur] = 'R';
}
else {
res[cur] = 'L';
}
}
else {
if(edg[cur][0] != i) {
res[cur] = 'R';
}
else {
res[cur] = 'L';
}
}
}
for(int i = 0 ; i < m; i++) {
assert(res[i] != '$');
cout << res[i];
}
cout << "\n";
}
signed main() {
fastio();
solve();
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
9048 KB |
Output is correct |
| 2 |
Incorrect |
6 ms |
9052 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
9048 KB |
Output is correct |
| 2 |
Incorrect |
6 ms |
9052 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
9048 KB |
Output is correct |
| 2 |
Incorrect |
6 ms |
9052 KB |
Output isn't correct |
| 3 |
Halted |
0 ms |
0 KB |
- |
