// In the name of Allah
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define all(x) (x).begin(),(x).end()
#define len(x) ((ll) (x).size())
#define F first
#define S second
#define pb push_back
#define sep ' '
#define endl '\n'
#define Mp make_pair
#define debug(x) cerr << #x << ": " << x << endl;
#define kill(x) cout << x << '\n', exit(0);
#define set_dec(x) cout << fixed << setprecision(x);
#define file_io(x,y) freopen(x, "r", stdin); freopen(y, "w", stdout);
int n, m;
const int maxn = 1e5 + 5;
const int maxlg = 20;
vector<pii> adj[maxn];
vector<pii> ques[maxn];
pii edgs[maxn];
vector<int> oedgs, nedgs;
bool mark[maxn];
int h[maxn], mn[maxn];
pii mq[maxn];
int st[maxn], ft[maxn];
int timer = 0;
int up[maxn][maxlg];
int col[maxn]; int c = 0;
char ans[maxn];
void pre_dfs(int v, int i = -1) {
mark[v] = 1; mn[v] = h[v];
for (auto f : adj[v]) {
int u = f.F, j = f.S;
if (!mark[u]) {
h[u] = h[v] + 1;
pre_dfs(u, j);
mn[v] = min(mn[v], mn[u]);
}
else if (j != i) {
mn[v] = min(mn[v], h[u]);
oedgs.pb(j);
}
}
if (mn[v] >= h[v] && i != -1) nedgs.pb(i);
else if (i != -1) oedgs.pb(i);
}
void dfs_col(int v) {
mark[v] = 1; col[v] = c;
for (auto f : adj[v]) {
int u = f.F, j = f.S;
if (!mark[u]) dfs_col(u);
}
}
void pre_dfsx(int v, int p = -1) {
mark[v] = 1;
st[v] = timer++;
up[v][0] = (p != -1) ? p : v;
for (int i = 1; i < maxlg; i++) {
up[v][i] = up[up[v][i - 1]][i - 1];
}
for (auto f : adj[v]) {
int u = f.F, j = f.S;
if (!mark[u]) pre_dfsx(u, v);
}
ft[v] = timer++;
}
bool is_gr(int u, int v) {
return (st[u] <= st[v] && ft[u] >= ft[v]);
}
int get_kgr(int v, int k) {
if (k == 0) return v;
int i = __builtin_ctz(k);
return get_kgr(up[v][i], k ^ (1 << i));
}
bool check(int v, int u, int k) {
int r = get_kgr(v, k);
return is_gr(r, u);
}
int get_lca(int v, int u) {
if (is_gr(v, u)) return v;
if (is_gr(u, v)) return u;
int l = 0, r = h[v] + 1;
while (r - l > 1) {
int mid = (l + r) / 2;
if (!check(v, u, mid)) l = mid;
else r = mid;
}
return get_kgr(v, r);
}
void solve_dfs(int v, int i = -1) {
mark[v] = 1; mq[v] = Mp(h[v], 0);
for (auto f : adj[v]) {
int u = f.F, j = f.S;
if (!mark[u]) {
h[u] = h[v] + 1;
solve_dfs(u, j);
if (mq[u].S != 0 && (mq[v].S == 0 || mq[u].F < mq[v].F)) {
mq[v] = mq[u];
}
}
}
for (auto f : ques[v]) {
int u = f.F, e = f.S;
if (mq[v].S == 0 || h[u] < mq[v].F) {
mq[v] = Mp(h[u], e);
}
}
if (mq[v].F < h[v] && mq[v].S != 0 && i != -1) {
if (mq[v].S == 1) {
if (v == col[edgs[i].F]) ans[i] = 'R';
else ans[i] = 'L';
}
else {
if (v == col[edgs[i].F]) ans[i] = 'L';
else ans[i] = 'R';
}
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n >> m;
for (int i = 0; i < m; i++) {
int u, v;
cin >> u >> v; u--; v--;
if (u != v) {
adj[u].pb(Mp(v, i)); adj[v].pb(Mp(u, i));
edgs[i] = Mp(u, v);
}
}
fill(mark, mark + n, 0);
for (int i = 0; i < n; i++) {
if (!mark[i]) pre_dfs(i);
}
for (int i = 0; i < n; i++) adj[i].clear();
for (int i : oedgs) {
int u = edgs[i].F, v = edgs[i].S;
adj[u].pb(Mp(v, i)); adj[v].pb(Mp(u, i));
}
fill(mark, mark + n, 0);
for (int i = 0; i < n; i++) {
if (!mark[i]) {
dfs_col(i); c++;
}
}
for (int i = 0; i < n; i++) adj[i].clear();
for (int i : nedgs) {
int u = col[edgs[i].F], v = col[edgs[i].S];
adj[u].pb(Mp(v, i)); adj[v].pb(Mp(u, i));
}
fill(mark, mark + n, 0);
for (int i = 0; i < c; i++) {
if (!mark[i]) pre_dfsx(i);
}
int q;
cin >> q;
for (int i = 0; i < q; i++) {
int u, v;
cin >> u >> v; u--; v--;
u = col[u]; v = col[v];
if (u == v) continue;
int r = get_lca(u, v);
if (r != u && r != v) {
ques[u].pb(Mp(r, 1)); ques[v].pb(Mp(r, 2));
}
else if (r == v) {
ques[u].pb(Mp(r, 1));
}
else if (r == u) {
ques[v].pb(Mp(r, 2));
}
}
fill(ans, ans + m, 'B');
fill(mark, mark + n, 0); fill(h, h + n, 0);
for (int i = 0; i < c; i++) {
if (!mark[i]) solve_dfs(i);
}
for (char ch : ans) cout << ch;
cout << endl;
return 0;
}
Compilation message
oneway.cpp: In function 'void dfs_col(int)':
oneway.cpp:61:16: warning: unused variable 'j' [-Wunused-variable]
61 | int u = f.F, j = f.S;
| ^
oneway.cpp: In function 'void pre_dfsx(int, int)':
oneway.cpp:76:16: warning: unused variable 'j' [-Wunused-variable]
76 | int u = f.F, j = f.S;
| ^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
5 ms |
5076 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
5 ms |
5076 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
5 ms |
5076 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
