Submission #1292859

#	Time	Username	Problem	Language	Result	Execution time	Memory
1292859		NHristov	One-Way Streets (CEOI17_oneway)	C++20	100 / 100	56 ms	19588 KiB

oneway

#include <bits/stdc++.h>
#define endl '\n'
using namespace std;
const int N=1e5+5, M=1e5+5;
int n, m, p, a[N], b[N], low[N], dep[N], c[N], d[N];
bool vis[N], bridge[M];
vector<int> g[N], t[N];

struct dsu {
    int p[N], sz[N];
    void init() {
        for(int i=1; i<=n; i++)
            p[i]=i, sz[i]=1;
    }
    int find(int u) {
        if(u==p[u])
            return u;
        return p[u]=find(p[u]);
    }
    void unite(int u, int v) {
        if((u=find(u))==(v=find(v)))
            return;
        if(sz[u]>sz[v])
            swap(u, v);
        sz[v]+=sz[u], p[u]=v;
    }
} dsu;

void dfs(int u, int p) {
    vis[u]=1;
    dep[u]=dep[p]+1;
    low[u]=dep[u];
    bool f=0;
    for(int e : g[u]) {
        int v=u^a[e]^b[e];
        if(v==p&&!f) {
            f=1;
            continue;
        }
        if(!vis[v]) {
            dfs(v, u);
            low[u]=min(low[u], low[v]);
            if(low[v]>dep[u])
                bridge[e]=1;
        }
        else
            low[u]=min(low[u], dep[v]);
    }
}
void dfs2(int u, int p) {
    for(int e : t[u]) {
        int v=u^a[e]^b[e];
        if(v==p)
            continue;
        d[v]=d[u]+1;
        dfs2(v, u);
        c[u]+=c[v];
    }
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    cin >> n >> m;
    for(int i=1; i<=m; i++) {
        cin >> a[i] >> b[i];
        g[a[i]].push_back(i);
        g[b[i]].push_back(i);
    }
    dsu.init();
    for(int i=1; i<=n; i++)
        if(!vis[i])
            dfs(i, 0);
    for(int i=1; i<=m; i++)
        if(!bridge[i])
            dsu.unite(a[i], b[i]);
    for(int i=1; i<=m; i++) {
        if(bridge[i]) {
            a[i]=dsu.find(a[i]), b[i]=dsu.find(b[i]);
            t[a[i]].push_back(i), t[b[i]].push_back(i);
        }
    }
    cin >> p;
    for(int i=1; i<=p; i++) {
        int u, v;
        cin >> u >> v;
        c[dsu.find(u)]++, c[dsu.find(v)]--;
    }
    for(int i=1; i<=n; i++) {
        if(dsu.p[i]==i&&!d[i]) {
            d[i]=1;
            dfs2(i, -1);
        }
    }
    for(int i=1; i<=m; i++) {
        if(!bridge[i]) {
            cout << "B";
            continue;
        }
        int u;
        if(d[a[i]]>d[b[i]])
            u=a[i];
        else
            u=b[i];
        if(c[u]==0)
            cout << "B";
        else {
            if((u==a[i]&&c[u]>0)||(u!=a[i]&&c[u]<0))
                cout << "R";
            else
                cout << "L";
        }
    }
    cout << endl;

    return 0;
}

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