#include<bits/stdc++.h>
//#define int long long
#define pii pair<int,int>
#define fi first
#define se second
/*#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")*/
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ldb = long double;
const ll N = (int)1e9 + 1;
const int maxN = (int)1e5 + 1;
const int mod = 1e9 + 7;
//const int mod = 998244353;
const ll infty = 1e18 + 7;
const int base = (int)4e5;
const int Block_size = 340;
void InputFile()
{
freopen("test.inp","r",stdin);
//freopen("scrivener.out","w",stdout);
//freopen("test.out","r",stdin);
}
void FastInput()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
}
int n,m,p;
int x[maxN],y[maxN];
vector<pii> adj1[maxN];
map<pii,int> apr;
char res[maxN];
int isbridge[maxN];
string juryoutput;
void Read()
{
//cin >> juryoutput;
cin >> n >> m;
for(int i = 1; i <= m; i++)
{
cin >> x[i] >> y[i];
res[i] = 'B';
if(x[i] == y[i])
{
continue;
}
if(apr[make_pair(min(x[i],y[i]),max(x[i],y[i]))] == 0)
{
adj1[x[i]].push_back({y[i],i});
adj1[y[i]].push_back({x[i],i});
}
apr[make_pair(min(x[i],y[i]),max(x[i],y[i]))]++;
}
}
int num[maxN],low[maxN];
int TimeDFS = 0;
void preDFS(int u,int pre)
{
num[u] = low[u] = ++TimeDFS;
for(pii x : adj1[u])
{
if(x.fi == pre) continue;
if(!num[x.fi])
{
preDFS(x.fi,u);
low[u] = min(low[u],low[x.fi]);
if(low[x.fi] == num[x.fi] && apr[ {min(u,x.fi),max(u,x.fi)}] == 1)
{
isbridge[x.se] = 1;
}
}
else
{
low[u] = min(low[u],num[x.fi]);
}
}
}
int isvis[maxN];
int cnt_grp = 0;
vector<vector<int>> adj2[maxN];
int grp[maxN];
/// 1 la phai
/// 0 la trai
void DFS_Build(int u)
{
isvis[u] = 1;
for(pii t : adj1[u])
{
if(isvis[t.fi]) continue;
if(isbridge[t.se])
{
cnt_grp++;
grp[t.fi] = cnt_grp;
if(u == x[t.se])
{
adj2[grp[u]].push_back({grp[t.fi],t.se,1});
adj2[grp[t.fi]].push_back({grp[u],t.se,0});
}
else
{
adj2[grp[u]].push_back({grp[t.fi],t.se,0});
adj2[grp[t.fi]].push_back({grp[u],t.se,1});
}
}
else grp[t.fi] = grp[u];
DFS_Build(t.fi);
}
}
int save_e[maxN];
int anc[25][maxN];
int dp[maxN];
int ifused[maxN];
int depth[maxN];
void DFS2(int u,int p)
{
for(vector<int> x : adj2[u])
{
int v = x[0];
if(v == p) continue;
depth[v] = depth[u] + 1;
save_e[v] = x[1];
if(x[2] == 1)
{
res[x[1]] = 'R';
}
else res[x[1]] = 'L';
anc[0][v] = u;
for(int i = 1; i <= (int)log2(n); i++)
{
anc[i][v] = anc[i-1][anc[i-1][v]];
}
DFS2(v,u);
}
}
void DFS3(int u,int p)
{
for(vector<int> x : adj2[u])
{
int v = x[0];
if(v == p) continue;
DFS3(v,u);
dp[u] += dp[v];
}
}
void DFS4(int u,int p)
{
for(vector<int> x : adj2[u])
{
int v = x[0];
if(v == p) continue;
DFS4(v,u);
ifused[u] += ifused[v];
}
}
int LCA(int u,int v)
{
if(depth[u] < depth[v]) swap(u,v);
int k = depth[u] - depth[v];
for(int i = (int)log2(n); i >= 0; i--)
{
if(k & (1 << i))
{
u = anc[i][u];
}
}
if(u == v) return u;
for(int i = (int)log2(n); i >= 0; i--)
{
if(anc[i][u] != anc[i][v])
{
u = anc[i][u];
v = anc[i][v];
}
}
return anc[0][u];
}
void Solve()
{
for(int i = 1; i <= n; i++)
{
if(!num[i])
{
preDFS(i,i);
}
}
for(int i = 1; i <= n; i++)
{
if(!isvis[i])
{
cnt_grp++;
grp[i] = cnt_grp;
DFS_Build(i);
}
}
/*for(int i = 1; i <= n; i++)
{
cout << grp[i] <<' ';
}
cout <<'\n'<<"dark";
return;*/
for(int i = 1; i <= cnt_grp; i++)
{
if(depth[i] == 0) DFS2(i,i);
}
cin >> p;
while(p--)
{
int a,b;
cin >> a >> b;
dp[LCA(grp[a],grp[b])]--;
dp[grp[a]]++;
ifused[LCA(grp[a],grp[b])]--;
ifused[grp[a]]++;
ifused[grp[b]]++;
}
//cout << save_e[2];return;
for(int i = 1; i <= cnt_grp; i++)
{
if(depth[i] == 0)
{
DFS3(i,i);
DFS4(i,i);
}
}
for(int i = 1; i <= cnt_grp; i++)
{
if(depth[i] == 0)
{
continue;
}
if(dp[i] > 0)
{
res[save_e[i]] = 'L' + 'R' - res[save_e[i]];
}
else if(ifused[i] == 0)
{
res[save_e[i]] = 'B';
}
}
string g;
for(int i = 1; i <= m; i++)
{
cout << res[i];
g.push_back(res[i]);
//if(res[i] != juryoutput[i-1]) {cout <<"sai o"<<' '<< i <<'\n';}
}
//cout << juryoutput <<'\n'<< g <<'\n';
//if(g == juryoutput) cout <<"OK";
//else cout <<"SAI CMNR";
}
void Debug()
{
}
int32_t main()
{
FastInput();
//InputFile();
//int sub_type;
//cin >> sub_type;
//Sieve();
//Prepare();
int test;
//cin >> test;
test = 1;
while(test--)
//for(int prc = 1; prc <= test; prc++)
{
Read();
Solve();
//Debug();
}
}
Compilation message
oneway.cpp: In function 'void InputFile()':
oneway.cpp:25:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
25 | freopen("test.inp","r",stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 2 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 3 |
Correct |
4 ms |
5204 KB |
Output is correct |
| 4 |
Incorrect |
4 ms |
5436 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 2 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 3 |
Correct |
4 ms |
5204 KB |
Output is correct |
| 4 |
Incorrect |
4 ms |
5436 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 2 |
Correct |
3 ms |
5076 KB |
Output is correct |
| 3 |
Correct |
4 ms |
5204 KB |
Output is correct |
| 4 |
Incorrect |
4 ms |
5436 KB |
Output isn't correct |
| 5 |
Halted |
0 ms |
0 KB |
- |
