#include <bits/stdc++.h>
#define all(s) s.begin(), s.end()
#define lb(s, a) lower_bound(all(s), (a)) - s.begin()
#define ii pair <int, int>
#define fi first
#define se second
using namespace std;
typedef long long ll;
const int ar = 2e5+2;
const ll mod = 1e9+7;
const int oo = 1e9;
int n, m;
int timeDfs = 0, scc = 0;
int low[ar], num[ar];
int id[ar];
bool deleted[ar], vs[ar];
vector <int> tplt[ar];
struct set3 {
int v, i, t;
};
vector <set3> g[ar];
stack <int> st;
void dfs(int u, int p) {
num[u] = low[u] = ++timeDfs;
st.push(u);
for (auto [v, i, t] : g[u]) if(v != p) {
if (deleted[v]) continue;
if (!num[v]){
dfs(v, u);
low[u] = min(low[u], low[v]);
}
else low[u] = min(low[u], num[v]);
}
if (low[u] == num[u]) {
scc++;
int v;
do {
v = st.top();
st.pop();
tplt[scc].push_back(v);
id[v] = scc;
deleted[v] = true;
}
while (v != u);
}
}
int h[ar], up[ar][18], val[ar];
ii par[ar];
void dfs2(int u, int p) {
for(auto x : tplt[u]) {
for(auto [v, i, t] : g[x]) {
v = id[v];
if(v == u || v == p) continue;
h[v] = h[u] + 1;
up[v][0] = u;
par[v] = {i, t};
for(int j = 1; j < 17; ++j)
up[v][j] = up[up[v][j - 1]][j - 1];
dfs2(v, u);
}
}
}
int lca(int u, int v) {
if(h[u] != h[id[v]]) {
if(h[u] < h[v]) swap(u, v);
int k = h[u] - h[v];
for(int j = 0; (1 << j) <= k; ++j)
if(k >> j & 1)
u = up[u][j];
}
if(u == v) return u;
int k = 31 - __builtin_clz(h[u]);
for(int j = k; j >= 0; --j)
if(up[u][j] != up[v][j]) {
u = up[u][j];
v = up[v][j];
}
return up[u][0];
}
void direct(int u, int p, int t) {
if(u == p) return;
while(u != p) {
val[par[u].fi] = par[u].se ^ t;
u = up[u][0];
}
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
#define task "CEOI17_ONEWAY"
if(fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
cin >> n >> m;
int u, v;
memset(val, -1, sizeof val);
for(int i = 1; i <= m; ++i) {
cin >> u >> v;
g[u].push_back({v, i, 0});
g[v].push_back({u, i, 1});
}
for(int i = 1; i <= n; ++i) if(id[i] == 0) {
dfs(i, 0);
dfs2(id[i], 0);
}
int q;
cin >> q;
while(q--) {
cin >> u >> v;
u = id[u]; v = id[v];
int p = lca(u, v);
direct(u, p, 0);
direct(v, p, 1);
}
for(int i = 1; i <= m; ++i)
if(val[i] == -1) cout << 'B';
else if(val[i] == 0) cout << 'L';
else cout << 'R';
}
Compilation message
oneway.cpp: In function 'int main()':
oneway.cpp:104:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
104 | freopen(task".inp", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:105:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
105 | freopen(task".out", "w", stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
4 ms |
10588 KB |
Output is correct |
| 2 |
Correct |
4 ms |
10608 KB |
Output is correct |
| 3 |
Runtime error |
12 ms |
29788 KB |
Execution killed with signal 11 |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
4 ms |
10588 KB |
Output is correct |
| 2 |
Correct |
4 ms |
10608 KB |
Output is correct |
| 3 |
Runtime error |
12 ms |
29788 KB |
Execution killed with signal 11 |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
4 ms |
10588 KB |
Output is correct |
| 2 |
Correct |
4 ms |
10608 KB |
Output is correct |
| 3 |
Runtime error |
12 ms |
29788 KB |
Execution killed with signal 11 |
| 4 |
Halted |
0 ms |
0 KB |
- |
