This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
const int NMAX = 100010;
const int LGMAX = 20;
namespace UF {
int tata[NMAX], g[NMAX];
int find(int x) {
if (tata[tata[x]] != tata[x])
tata[x] = find(tata[x]);
return tata[x];
}
bool unite(int a, int b) {
a = find(a);
b = find(b);
if (a == b)
return 0;
if (g[a] < g[b])
swap(a, b);
tata[b] = a, g[a] += g[b];
return 1;
}
void UF(int n) {
fill(g, g + n + 1, 1);
iota(tata, tata + n + 1, 0);
}
}
bool in_cicle[NMAX];
char ans[NMAX];
vector <pair <int, int>> adia[NMAX];
int muchie_tata[NMAX];
int stramos[LGMAX][NMAX];
int h[NMAX];
int lazy[LGMAX][NMAX];
// for push: 0->nimic, 1->vreau in sus, 2->vreau in jos, 4->sunt in ciclu
void dfs(int nod, int tata)
{
stramos[0][nod] = tata;
h[nod] = 1 + h[tata];
for (int i = 1; i < LGMAX; i++)
stramos[i][nod] = stramos[i - 1][stramos[i - 1][nod]];
for (auto i : adia[nod]) {
if (i.first == tata)
muchie_tata[nod] = i.second;
else
dfs(i.first, nod);
}
}
int lca(int a, int b)
{
if (h[a] < h[b])
swap(a, b);
for (int i = LGMAX - 1; i >= 0; i--)
if (h[a] - (1 << i) >= h[b])
a = stramos[i][a];
if (a == b)
return a;
for (int i = LGMAX - 1; i >= 0; i--)
if (stramos[i][a] != stramos[i][b])
a = stramos[i][a], b = stramos[i][b];
return stramos[0][a];
}
void push_on_chain(int from, int to, int val)
{
/// to este NEAPARAT stramos de-al lui from
int l = h[from] - h[to];
for (int i = LGMAX - 1; i >= 0; i--) {
if (l >= (1 << i)) {
lazy[i][from] |= val;
from = stramos[i][from];
l -= (1 << i);
}
}
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m, a, b;
cin >> n >> m;
UF::UF(n);
vector <pair <int, int>> useless;
for (int i = 1; i <= m; i++) {
cin >> a >> b;
if (!UF::unite(a, b)) {
/// am un ciclu
useless.push_back({ a, b });
in_cicle[i] = 1;
ans[i] = 'B';
}
else {
adia[a].push_back({ b, i });
adia[b].push_back({ a, -i });
}
}
for (int i = 1; i <= n; i++)
if (UF::find(i) == i)
dfs(i, 0);
for (auto i : useless) {
int l = lca(i.first, i.second);
push_on_chain(i.first, l, 4);
push_on_chain(i.second, l, 4);
}
int q;
cin >> q;
while (q--) {
cin >> a >> b;
/// vreau sa ma duc de la a la b
int l = lca(a, b);
push_on_chain(a, l, 1);
push_on_chain(b, l, 2);
}
for (int i = LGMAX - 1; i; i--) {
for (int j = 1; j <= n; j++) {
lazy[i - 1][j] |= lazy[i][j];
lazy[i - 1][stramos[i - 1][j]] |= lazy[i][j];
}
}
for (int i = 1; i <= n; i++) {
if (muchie_tata[i] == 0)
continue;
bool sus = (lazy[0][i] & 1);
bool jos = (lazy[0][i] & 2);
int id = muchie_tata[i];
int rev = (id < 0);
id = abs(id);
in_cicle[id] = (lazy[0][i] & 4);
if (in_cicle[id])
ans[id] = 'B';
else {
assert(!sus || !jos);
if (sus)
ans[id] = "RL"[rev];
else if (jos)
ans[id] = "LR"[rev];
else
ans[id] = 'B';
}
}
for (int i = 1; i <= m; i++)
cout << ans[i];
cout << '\n';
return 0;
}/*
5 6
1 2
1 2
4 3
2 3
1 3
5 1
2
4 5
1 3*/
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