Submission #795228

#	Time	Username	Problem	Language	Result	Execution time	Memory
795228		bLIC	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	273 ms	56128 KiB

oneway

/**
 *  Author: Anil Byar
**/

#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>

// using namespace __gnu_pbds;
using namespace std;

// template<class T>
// using ordered_set = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;



#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)(x).size()
#define uniq(v) v.erase(unique(all(v)), v.end())
#define ft first
#define sd second
#define pb push_back
#define eb emplace_back

// Source: https://codeforces.com/blog/entry/68809
// { start
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '"' << x << '"';}
void __print(const string &x) {cerr << '"' << x << '"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
// } end


typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<ll> vl;
typedef vector<pll> vll;
typedef vector<vi> vvi;
typedef vector<vii> vvii;
typedef vector<vl> vvl;

#define dbg if(0)

const ll MOD = 1e9+7;
const ll MOD9 = 998244353;
const ll INFLL = 1e18+5;
const int INF = 1e9;

void printbit(int x, int len) {string s="\n";while(len--){s=((x%2)?'1':'0')+s;x/=2;} cout<<s;}
ll power(ll x, ll y, ll mod){if (y==0) return 1;ll ret = power(x, y/2, mod);ret *= ret;ret%=mod;if (y&1) ret *= x;return ret%mod;}
ll modinv(ll x, ll mod = MOD) {return power(x, mod-2, mod);}

template<class T> bool chmin(T& a, T b){return (a>b?a=b,1:0);}
template<class T> bool chmax(T& a, T b){return (a<b?a=b,1:0);}
template<class T>
istream& operator>>(istream&in, vector<T>&v){
    for (T& x:v) in>>x;
    return in;
}
template<class T>
ostream& operator<<(ostream&out, vector<T>&v){
    for (T& x:v) out<<x<<' ';
    cout<<'\n';
    return out;
}
// use ?: with brackets (?:)
// check for overflow
// think about dp
// Read the statement carefully

struct Edge{
    int to, id;// wt
    bool dir;
};

const int N = 1e5;

vector<Edge> adj[N];
bool visNode[N];
bool visEdge[N];

int dpUp[N];

set<int> startsends[N];
string ans;

void dfs(int node, int edgeId, bool dir){
    visNode[node] = true;
    // debug(node);
    for (Edge e:adj[node]){
        
        // handles cases of multiple edges
        if (e.id==edgeId) continue;
        if (!visEdge[e.id]){
            visEdge[e.id] = true;
            if (!visNode[e.to]){
                dfs(e.to, e.id, e.dir);
                dpUp[node] += dpUp[e.to];

                if (sz(startsends[node])<sz(startsends[e.to])) swap(startsends[node], startsends[e.to]);
                for (int x:startsends[e.to]) {
                    if (startsends[node].count(-x)) startsends[node].erase(-x);
                    else startsends[node].insert(x);
                }
            } else {
                dpUp[node]++;
                ans[e.id] = 'B';
            }
        } else {
            dpUp[node]--;
        }
    }
    if (edgeId!=-1){
        if (sz(startsends[node])==0 || dpUp[node]) ans[edgeId] = 'B';
        else ans[edgeId] = ((dir^(*startsends[node].begin()<0))?'R':'L');
    }
    // debug(node, dpUp[node], startsends[node]);
}


void solve(){
    int n, m;cin>>n>>m;
    ans.resize(m,'\0');
    for (int i = 0;i<m;i++){
        int u, v;cin>>u>>v;
        u--;v--;
        adj[u].push_back({v, i, 0}); // u -> v
        adj[v].push_back({u, i, 1}); // v -> u
    }
    int q;cin>>q;
    for (int i = 0;i<q;i++) {
        int u, v;cin>>u>>v;
        u--;v--;
        if (u==v) continue;
        startsends[u].insert(i+1);  // start
        startsends[v].insert(-i-1); // end
    }
    for (int i = 0;i<n;i++){
        if (!visNode[i]){
            dfs(i, -1, 0);
        }
    }
    cout<<ans;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);


#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
    freopen("input.in", "r", stdin);
    freopen("output.out", "w", stdout);
    freopen("debug.dbg", "w", stderr);
    int tt = clock();
#endif

    int t=1, i = 1;
    // cin>>t;
    while(t--){
        // cout<<"Case #"<<i++<<": ";
        solve();
        cout<<'\n';
    }
#ifndef ONLINE_JUDGE
    cerr << "TIME = " << (float)(clock() - tt)/CLOCKS_PER_SEC << endl;
    tt = clock();
#endif
}

Compilation message (stderr)

oneway.cpp: In function 'int main()':
oneway.cpp:186:14: warning: unused variable 'i' [-Wunused-variable]
  186 |     int t=1, i = 1;
      |              ^

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40