Submission #988493

#	Time	Username	Problem	Language	Result	Execution time	Memory
988493		steveonalex	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	78 ms	24144 KiB

oneway

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
 
#define MASK(i) (1ULL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
 
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
 
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ll mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
 
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
 
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }
 
template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }
 
template <class T>
    void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
        for(auto item: container) out << item << separator;
        out << finish;
    }
 
template <class T>
    void remove_dup(vector<T> &a){
        sort(ALL(a));
        a.resize(unique(ALL(a)) - a.begin());
    }

const int N = 1e5 + 69;
int n, m, p;
vector<int> graph[N];
int low[N], num[N], topo[N];
deque<int> st;
pair<int, int> edge[N];

void dfs(int u, int p){
    num[u] = low[u] = ++num[0];
    st.push_back(u);
    for(int v: graph[u]) {
        if (v == p){p = -1; continue;}
        if (!num[v]){
            dfs(v, u);
            minimize(low[u], low[v]);
        }
        else minimize(low[u], num[v]);
    }

    if (num[u] == low[u]){
        topo[0]++;
        while(st.back() != u){
            topo[st.back()] = topo[0];
            st.pop_back();
        }
        st.pop_back();
        topo[u] = topo[0];
    }
}

vector<pair<int, int>> bridge_tree[N];
pair<int, int> par[N];
int h[N];

void go(int u, int p){
    h[u] = h[p] + 1;
    for(pair<int, int> v: bridge_tree[u]) if (v.first != p){
        par[v.first] = {u, v.second};
        go(v.first, u);
    }
}

struct DSU{
    int n;
    vector<int> parent, sz, mi;

    DSU(int _n){
        n = _n;
        parent.resize(n+1); sz.resize(n+1, 1);
        for(int i = 1; i<=n; ++i) parent[i] = i;
        mi = parent;
    }

    int find_set(int u){return (u == parent[u]) ? u : (parent[u] = find_set(parent[u]));}
    bool same_set(int u, int v){return find_set(u) == find_set(v);}

    bool join_set(int u, int v){
        u = find_set(u), v = find_set(v);
        if (u != v){
            if (sz[u] < sz[v]) {swap(u, v); mi[u] = mi[v];}
            parent[v] = u;
            sz[u] += sz[v];
            return true;
        }
        return false;
    }

    int get_size(int u){return sz[find_set(u)];}

    int get_mi(int u){return mi[find_set(u)];}
};

int main(void){
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
    cin >> n >> m;
    for(int i = 0; i<m; ++i){
        int u, v; cin >> u >> v;
        edge[i] = {u, v};
        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    for(int i = 1; i<=n; ++i) if (num[i] == 0) {
        dfs(i, 0);
    }

    string ans(m, 'B');
    for(int i = 0; i<m; ++i){
        int u = edge[i].first, v = edge[i].second;
        u = topo[u], v = topo[v];
        if (u == v) continue;
        bridge_tree[u].push_back({v, i});
        bridge_tree[v].push_back({u, i});
    }

    for(int i = 1; i<=topo[0]; ++i) if (h[i] == 0) {
        go(i, 0);
    }

    cin >> p;

    DSU mst(topo[0]);
    for(int i = 0; i<p; ++i){
        int u, v; cin >> u >> v;
        u = topo[u], v = topo[v];
        u = mst.get_mi(u); v = mst.get_mi(v);
        while(u != v){
            if (h[u] > h[v]){
                ans[par[u].second] = 'R';
                mst.join_set(par[u].first, u);
                u = mst.get_mi(u);
            }
            else{
                ans[par[v].second] = 'L';
                mst.join_set(par[v].first, v);
                v = mst.get_mi(v);
            }
        }
    }

    for(int i= 0; i<m; ++i) if (ans[i] != 'B'){
        bool to_root = (ans[i] == 'R');
        int u = edge[i].first, v = edge[i].second;
        u = topo[u], v = topo[v];
        if ((h[u] > h[v]) == to_root) ans[i] = 'R';
        else ans[i] = 'L';
    }

    cout << ans << "\n";


    return 0;
}

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