Submission #986270

#	Time	Username	Problem	Language	Result	Execution time	Memory
986270		Do_you_copy	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	90 ms	39108 KiB

oneway

    #include <bits/stdc++.h>
    //#define int long long
    #define fi first
    #define se second
    #define pb push_back
    #define faster ios_base::sync_with_stdio(0); cin.tie(0);
    using namespace std;
    using ll = long long;
    using ull = unsigned ll;
    using ld = long double;
    using pii = pair <int, int>;
    using pil = pair <int, ll>;
    using pli = pair <ll, int>;
    using pll = pair <ll, ll>;
    mt19937 Rand(chrono::steady_clock::now().time_since_epoch().count());
     
    ll min(const ll &a, const ll &b){
        return (a < b) ? a : b;
    }
     
    ll max(const ll &a, const ll &b){
        return (a > b) ? a : b;
    }
     
    //const ll Mod = 1000000007;
    //const ll Mod2 = 999999999989;
    //only use when required
    const int maxN = 2e5 + 1;
    int n, m, k;
     
    struct TDSU{
        vector <pii> save;
        vector <int> lab;
        TDSU(){}
        TDSU(int _n){
            lab.resize(_n, -1);
        }
        inline void resize(int _n){
            lab.resize(_n, -1);
        }
        inline int find_set(int u){
            if (lab[u] < 0) return u;
            return lab[u] = find_set(lab[u]);
        }
        inline int find(int u){
            if (lab[u] < 0) return u;
            return find(lab[u]);
        }
        inline void merge(int u, int v){
            if (lab[u] > lab[v]) swap(u, v);
            save.pb({v, lab[v]});
            lab[u] += lab[v];
            lab[v] = u;
        }
        inline void undo(){
     
            int v = save.back().fi;
            int u = lab[v];
            lab[v] = save.back().se;
            lab[u] -= lab[v];
            save.pop_back();
        }
        inline void clear(){
            lab.clear();
            save.clear();
        }
        inline void reset(int _n){
            clear();
            resize(_n);
        }
        inline void roll_back(int _n){
            while (save.size() > _n) undo();
        }
    };
    TDSU dsu;
    int timedfs, low[maxN], num[maxN];
    int id[maxN];
    int mark[maxN];
    int node_cnt;
     
    struct TEdge{
        int u, v, idx;
    };
    TEdge e[maxN];
    vector <TEdge> adj[maxN];
     
    void dfs(int u, int idx){
        low[u] = num[u] = ++timedfs;
        for (auto i: adj[u]){
            int v = i.u ^ i.v ^ u;
            if (i.idx == idx) continue;
            if (!num[v]){
                dfs(v, i.idx);
                low[u] = min(low[u], low[v]);
                if (low[v] == num[v]) mark[i.idx] = 1;
            }
            else{
                low[u] = min(low[u], num[v]);
            }
        }
    }
     
    vector <pii> adj1[maxN];
    int lift[maxN][20];
    int depth[maxN];
    int val[maxN];
     
    void dfs1(int u, int p){
        lift[u][0] = p;
        depth[u] = depth[p] + 1;
        for (int i = 1; i < 20; ++i){
            lift[u][i] = lift[lift[u][i - 1]][i - 1];
            if (!lift[u][i]) break;
        }
        for (auto i: adj1[u]){
            int v = i.fi;
            if (v == p) continue;
            dfs1(v, u);
        }
    }
     
    int lca(int u, int v){
        if (depth[u] < depth[v]) swap(u, v);
        int k = depth[u] - depth[v];
        while (k){
            int t = k & -k;
            u = lift[u][__lg(t)];
            k -= t;
        }
        if (u == v) return u;
        for (int i = 19; i >= 0; --i){
            if (lift[u][i] != lift[v][i]){
                u = lift[u][i];
                v = lift[v][i];
            }
        }
        return lift[u][0];
    }
     
    void dfs2(int u, int p){
        for (auto i: adj1[u]){
            int v = i.fi;
            if (v == p) continue;
            dfs2(v, u);
            val[u] += val[v];
        }
    }
     
    void Init(){
        cin >> n >> m;
        for (int i = 1; i <= m; ++i){
            cin >> e[i].u >> e[i].v;
            e[i].idx = i;
            adj[e[i].u].pb(e[i]);
            adj[e[i].v].pb(e[i]);
        }
        for (int i = 1; i <= n; ++i){
            if (!num[i]) dfs(i, 0);
        }
        dsu.resize(n + 1);
        vector <int> bridge;
        for (int i = 1; i <= m; ++i){
            if (!mark[i]){
                int x = dsu.find_set(e[i].u);
                int y = dsu.find_set(e[i].v);
                if (x != y){
                    dsu.merge(x, y);
                }
            }
            else bridge.pb(i);
        }
        for (int i = 1; i <= n; ++i){
            int j = dsu.find_set(i);
            if (!id[j]) id[j] = ++node_cnt;
            id[i] = id[j];
        }
        for (int i: bridge){
            int u = id[e[i].u];
            int v = id[e[i].v];
            adj1[u].pb({v, i});
            adj1[v].pb({u, -i});
        }
        for (int i = 1; i <= node_cnt; ++i){
            if (!lift[i][0]){
                dfs1(i, 0);
            }
        }
        cin >> k;
        for (int i = 1; i <= k; ++i){
            int u, v;
            cin >> u >> v;
            u = id[u];
            v = id[v];
            ++val[u];
            --val[v];
        }
        for (int i = 1; i <= node_cnt; ++i){
            if (!lift[i][0]){
                dfs2(i, 0);
            }
        }
        for (int i = 1; i <= m; ++i){
            int x = id[e[i].u];
            int y = id[e[i].v];
            if (x == y) cout << "B";
            if(depth[x]>depth[y]){
                if(!val[x]) cout<<"B";
                if(val[x] > 0) cout<<"R";
                if(val[x] < 0) cout<<"L";
            }
            if(depth[x] < depth[y]){
                if(!val[y]) cout<<"B";
                if(val[y] > 0) cout<<"L";
                if(val[y] < 0) cout<<"R";
            }
        }
    }
     
    #define debu
    #define taskname "test"
    signed main(){
        if (fopen(taskname".inp", "r")){
            freopen(taskname".inp", "r", stdin);
            #ifdef debug
            freopen(taskname".out", "w", stdout);
            #endif
        }
        faster;
        ll tt = 1;
        //cin >> tt;
        while (tt--){
            Init();
        }
        if (fopen("timeout.txt", "r")){
            ofstream timeout("timeout.txt");
            timeout << 1000 * double(clock()) / CLOCKS_PER_SEC;
            #ifndef debug
            cerr << "\nTime elapsed: " << 1000 * double(clock()) / CLOCKS_PER_SEC << "ms\n";
            #endif
        }
    }

Compilation message (stderr)

oneway.cpp: In member function 'void TDSU::roll_back(int)':
oneway.cpp:72:32: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   72 |             while (save.size() > _n) undo();
      |                    ~~~~~~~~~~~~^~~~
oneway.cpp: In function 'int main()':
oneway.cpp:223:20: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  223 |             freopen(taskname".inp", "r", stdin);
      |             ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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