Submission #627110

#	Time	Username	Problem	Language	Result	Execution time	Memory
627110		Do_you_copy	One-Way Streets (CEOI17_oneway)	C++17	60 / 100	103 ms	28732 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 = 1e5 + 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];
        if (!val[v]){
            mark[abs(i.se)] = 0;
        }
        else if (val[v] * i.se < 0) mark[abs(i.se)] = 1;
        else mark[abs(i.se)] = -1;
    }
}

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);
                //cerr << e[i].u << " " << e[i].v << "?\n";
            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){
        if (!mark[i]) cout << 'B';
        else if (mark[i] < 0) cout << 'L';
        else 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:72:28: 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:220:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  220 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 0 / 40