Submission #1118657

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118657		vjudge1	One-Way Streets (CEOI17_oneway)	C++17	0 / 100	3 ms	9056 KiB

oneway

#include <bits/stdc++.h>

#define fi first
#define se second

using namespace std;

const int N = 1e5;
const int LogN = 31 - __builtin_clz(N);

int n, m, nQuery, lab[N + 2], h[N + 2], par[N + 2][LogN + 2], lgn, num[N + 2], low[N + 2],
    group[N + 2], timeDFS = 0, nGroup = 0, dir[N + 2][2];

bool bridge[N + 2];

vector<pair<int, int> > fadj[N + 2];

vector<int> adj[N + 2];

pair<int, int> edge[N + 2], que[N + 2];

void input() {
    cin >> n >> m;
    int u, v;
    for(int i = 1; i <= m; i++) {
        cin >> u >> v;
        edge[i] = make_pair(u, v);
        fadj[u].push_back(make_pair(v, i));
        fadj[v].push_back(make_pair(u, i));
    }
    cin >> nQuery;
    for(int i = 1; i <= nQuery; i++) {
        cin >> que[i].fi >> que[i].se;
    }
}

int getRoot(int u) {
    return lab[u] < 0 ? u : lab[u] = getRoot(lab[u]);
}

bool unite(int u, int v) {
    u = getRoot(u);
    v = getRoot(v);
    if(u == v) return false;
    if(lab[u] > lab[v]) swap(u, v);
    lab[u] += lab[v];
    lab[v] = u;
    return true;
}

void DFS(int u) {
    for(int v : adj[u]) {
        if(v == par[u][0]) continue;
        h[v] = h[u] + 1;
        par[v][0] = u;
        for(int j = 1; j <= lgn; j++) par[v][j] = par[par[v][j - 1]][j - 1];
        DFS(v);
    }
}

int getLCA(int u, int v) {
    if(h[u] != h[v]) {
        if(h[u] < h[v]) swap(u, v);
        int dif = h[u] - h[v];
        for(int i = 0; (1 << i) <= dif; i++) {
            if((dif >> i) & 1) u = par[u][i];
        }
    }
    if(u == v) return u;
    for(int j = lgn; j >= 0; j--) {
        if(par[u][j] == par[v][j]) continue;
        u = par[u][j];
        v = par[v][j];
    }
    return par[u][0];
}

void tarjan(int u, int p) {
    num[u] = low[u] = ++timeDFS;
    for(pair<int, int> e : fadj[u]) {
        int v = e.fi;
        int id = e.se;
        if(id == p) continue;
        if(num[v]) low[u] = min(low[u], num[v]);
        else {
            tarjan(v, id);
            low[u] = min(low[u], low[v]);
            if(low[v] == num[v]) bridge[id] = 1;
        }
    }
}

void calc(int u) {
    for(int v : adj[u]) {
        if(v == par[u][0]) continue;
        calc(v);
        dir[u][0] += dir[v][0];
        dir[u][1] += dir[v][1];
    }
}

void solve() {
    lgn = 31 - __builtin_clz(n);
    for(int i = 1; i <= n; i++) {
        if(!num[i]) tarjan(i, 0);
    }
    memset(lab, -1, sizeof lab);
    for(int i = 1; i <= m; i++) {
        if(bridge[i]) {
            continue;
        }
        int u = edge[i].fi;
        int v = edge[i].se;
        unite(u, v);
    }
    for(int i = 1; i <= n; i++) {
        if(lab[i] < 0) group[i] = ++nGroup;
    }
    for(int i = 1; i <= n; i++) {
        group[i] = group[getRoot(i)];
    }
    for(int i = 1; i <= m; i++) {
        if(bridge[i]) {
            adj[group[edge[i].fi]].push_back(group[edge[i].se]);
            adj[group[edge[i].se]].push_back(group[edge[i].fi]);
        }
    }
    for(int i = 1; i <= nGroup; i++) {
        if(par[i][0] == 0) DFS(i);
    }
    for(int i = 1; i <= nQuery; i++) {
        int u = group[que[i].fi];
        int v = group[que[i].se];
        int lca = getLCA(u, v);
        dir[u][0]++;
        dir[v][1]++;
        dir[lca][0]--;
        dir[lca][1]--;
    }
    for(int i = 1; i <= nGroup; i++) {
        if(par[i][0]) calc(i);
    }
    for(int i = 1; i <= m; i++) {
        if(!bridge[i]) {
            cout << 'B';
            continue;
        }
        int u = group[edge[i].fi];
        int v = group[edge[i].se];
        if(h[u] < h[v]) {
            if(dir[v][0] > 0) cout << 'L';
            else if(dir[v][1] > 0) cout << 'R';
            else cout << 'B';
        } else {
            if(dir[u][0] > 0) cout << 'R';
            else if(dir[u][1] > 0) cout << 'L';
            else cout << 'B';
        }
    }
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
//    freopen(" .inp", "r", stdin);
//    freopen(" .out", "w", stdout);
    input();
    solve();
    return 0;
}

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