#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#define deb(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<typename ...Args>
void logger(string vars, Args&&... values) {
cerr<<vars<<" = ";
string delim="";
(...,(cerr<<delim<<values,delim=", "));
cerr<<"\n";
}
#else
#define deb(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<typename ...Args>
void logger(string vars, Args&&... values) {}
#endif
#define pb push_back
#define sz(x) (int)(x.size())
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<typename T> inline void maxa(T& a,T b){a=max(a,b);}
template<typename T> inline void mina(T& a,T b){a=min(a,b);}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int mxN=1e5+5; //make sure this is right
const int mod=1e9+7;
struct edge{
int to,d,i;
};
vector<edge> graph[mxN],tree[mxN];
int lo[mxN],id[mxN],cur,up[mxN][20],sum[mxN][2],ht[mxN],ans[mxN],seen[mxN];
struct DSU{
int uf[mxN];
void init(){memset(uf,-1,sizeof(uf));}
int find(int x){return uf[x]<0?x:uf[x]=find(uf[x]);}
bool same(int x,int y){return find(x)==find(y);}
void unite(int x,int y){
x=find(x); y=find(y);
if(x==y)
return;
if(uf[x]>uf[y])
swap(x,y);
if(sz(tree[y])>sz(tree[x]))
swap(tree[y],tree[x]);
for(auto &u:tree[y])
tree[x].pb(u);
tree[y].clear();
uf[x]+=uf[y]; uf[y]=x;
}
} dsu;
void dfs(int at,int p){
lo[at]=id[at]=++cur;
for(auto &[to,d,i]:graph[at]){
if(i==p)
continue;
if(!lo[to])
dfs(to,i);
if(lo[to]>id[at]){
tree[dsu.find(at)].pb({dsu.find(to),d,i});
tree[dsu.find(to)].pb({dsu.find(at),d,i});
} else{
dsu.unite(at,to);
}
mina(lo[at],lo[i]);
}
}
void dfs2(int at,int p){
up[at][0]=~p?p:at;
for(int i=1;i<20;i++)
up[at][i]=up[up[at][i-1]][i-1];
for(auto &[to,d,i]:tree[at]){
to=dsu.find(to);
if(to==p)
continue;
ht[to]=ht[at]+1;
dfs2(to,at);
}
}
int jump(int a,int k){
for(int i=0;i<20;i++){
if(k&(1<<i))
a=up[a][i];
}
return a;
}
int lca(int a,int b){
if(ht[a]>ht[b])
swap(a,b);
b=jump(b,ht[b]-ht[a]);
if(a==b)
return a;
for(int i=19;i>=0;i--){
if(up[a][i]!=up[b][i]){
a=up[a][i];
b=up[b][i];
}
}
return up[a][0];
}
void dfs3(int at,int p){
seen[at]=1;
for(auto &[to,d,i]:tree[at]){
to=dsu.find(to);
if(to==p)
continue;
dfs3(to,at);
assert(!(sum[to][0] && sum[to][1]));
if(sum[to][0]){
ans[i]=d?1:2;
} else if(sum[to][1]){
ans[i]=d?2:1;
}
sum[at][0]+=sum[to][0];
sum[at][1]+=sum[to][1];
}
}
int main(){
cin.sync_with_stdio(0);
cin.tie(0); cout.tie(0);
#ifdef LOCAL
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
#endif
dsu.init();
int n,m; cin>>n>>m;
for(int i=0;i<m;i++){
int a,b; cin>>a>>b;
graph[a].pb({b,1,i});
graph[b].pb({a,0,i});
}
for(int i=1;i<=n;i++){
if(!lo[i]) dfs(i,-1);
}
for(int i=1;i<=n;i++){
set<int> has;
vector<edge> ac;
for(auto &u:tree[i]){
if(has.count(u.i))
continue;
has.insert(u.i);
ac.pb(u);
}
swap(tree[i],ac);
}
for(int i=1;i<=n;i++){
if(!ht[i] && sz(tree[i])) dfs2(i,-1);
}
int q; cin>>q;
while(q--){
int a,b; cin>>a>>b;
a=dsu.find(a);
b=dsu.find(b);
int p=lca(a,b);
sum[a][0]++;
sum[p][0]--;
sum[b][1]++;
sum[p][1]--;
}
for(int i=1;i<=n;i++){
if(!seen[i] && sz(tree[i])) dfs3(i,-1);
}
string s="BLR";
for(int i=0;i<m;i++) cout<<s[ans[i]];
}
Compilation message
oneway.cpp: In function 'void dfs(int, int)':
oneway.cpp:61:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
61 | for(auto &[to,d,i]:graph[at]){
| ^
oneway.cpp: In function 'void dfs2(int, int)':
oneway.cpp:80:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
80 | for(auto &[to,d,i]:tree[at]){
| ^
oneway.cpp: In function 'void dfs3(int, int)':
oneway.cpp:114:15: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
114 | for(auto &[to,d,i]:tree[at]){
| ^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
5456 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
5456 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
5456 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
