Submission #321761

#	Time	Username	Problem	Language	Result	Execution time	Memory
321761		Karen124	One-Way Streets (CEOI17_oneway)	C++14	0 / 100	2 ms	2796 KiB

oneway

#include <bits/stdc++.h>
     
using namespace std;
     
#define ll long long int 
#define F first
#define S second
#define pb push_back
 
const ll N = 1e5 + 10;
const ll LOG = 20;
const ll MOD = 1e9 + 7;
const ll INF = 1e9 + 10;
struct Edge{
    int u, v;
} e[N];
int n, m, p, a[N], b[N], h[N], mn[N], pr[N], sz[N], par[LOG][N], up[N], dn[N];
vector < pair <int, int> > adj[N];
vector <int>  E;
bool mrk[N], is[N];
int rev[N];
void dfs(int v, int i){
    mrk[v] = 1; mn[v] = h[v];
    for (auto it : adj[v]){
        int u = it.F, j = it.S;
        if (!mrk[u]){
            h[u] = h[v] + 1;
            dfs(u, j);
            mn[v] = min(mn[u], mn[v]);
        }
        else if (i != j){
            mn[v] = min(mn[v], h[u]);   
        }
    }
    if(mn[v] == h[v] && i){
        E.pb(i);
        is[i] = 1;
    }
    return;
}
int find(int v){
    if (pr[v] == v) return v;
    return (pr[v] = find(pr[v]));
}
void prepare(){
    for (int i = 1; i <= n; i++){
        pr[i] = i;
        sz[i] = 1;
    }
    return;
}
void merge(int u, int v){
    u = find(u); v = find(v);
    if (u == v) return;
    if (sz[v] < sz[u]) swap(u, v);
    pr[u] = v;
    sz[v] += sz[u];
    return;
}
void dfs_cal(int v, int prpr){
    for (auto it : adj[v]){
        int u = it.F;
        if (u != prpr){
            par[0][u] = v;
            h[u] = h[v] + 1;
            dfs_cal(u, v);
        }
    }
    for (int i = 1; i < LOG; i++){
        par[i][v] = par[i - 1][par[i - 1][v]];
    }
    return;
}
int get_pr(int v, int dif){
    for (int i = 0; i < LOG; i++){
        if ((dif >> i) & 1){
            v = par[i][v];
        }
    }
    return v;
}
int lca(int u, int v){ 
    if (h[v] < h[u]) swap(u, v);
    v = get_pr(v, h[v] - h[u]);
    if (u == v) return v;
    for (int i = LOG - 1; i >= 0; i--){
        if (par[i][u] != par[i][v]){
            u = par[i][u];
            v = par[i][v];
        }
    }
    return par[0][v];
}
void dfs_up(int v, int prpr, int i){
    for (auto it : adj[v]){
        int u = it.F, j = it.S;
        if (u == prpr) continue;
        dfs_up(u, v, j);
        up[v] += up[u];
    }
    if (i && up[v]) rev[i] = 1 + (e[i].u != v);
    return;
}
void dfs_dn(int v, int prpr, int i){
    for (auto it : adj[v]){
        int u = it.F, j = it.S;
        if (u == prpr) continue;
        dfs_dn(u, v, j);
        dn[v] += dn[u];
    }
    if (i && dn[v]) rev[i] = 1 + (e[i].u == v);
    return;
}
int main() {
    cin >> n >> m;
    for (int i = 1; i <= m; i++){
        cin >> e[i].u >> e[i].v;
        adj[e[i].u].pb({e[i].v, i});
        adj[e[i].v].pb({e[i].u, i});
    }
    dfs(1, 0);
    cin >> p;
    for (int i = 1; i <= p; i++){
        cin >> a[i] >> b[i];
    }
    prepare();
    for (int i = 1; i <= m; i++){
        if (!is[i]){
            merge(e[i].u, e[i].v);
        }
    }
    for (int i = 1; i <= n; i++) adj[i].clear();
    for (int i : E){
        adj[find(e[i].u)].pb({find(e[i].v), i});
        adj[find(e[i].v)].pb({find(e[i].u), i});
    }
    fill(h, h + n + 1, 0);
    dfs_cal(find(1), 0);
    for (int i = 1; i <= p; i++){
        if (find(a[i]) == find(b[i])){
            continue;
        }
        int LCA = lca(a[i], b[i]);
        if (LCA == a[i]){
            dn[b[i]]++;
            dn[LCA] --;
        }
        if (LCA == b[i]){
            up[a[i]]++;
            up[LCA]--;
        }
        else {
            up[a[i]]++; up[LCA]--;
            dn[b[i]]++; dn[LCA]--;
        }
    }
    dfs_up(find(1), 0, 0);
    dfs_dn(find(1), 0, 0);
    for (int i = 1; i <= m; i++){
        if (!is[i]) cout << "B";
        else if (rev[i] == 1) cout << "R";
        else if (rev[i] == 2) cout << "L";
        else cout << "B";
    }
    cout << '\n';
    return 0;
}
/*
5 6
1 2
1 2
4 3
2 3
1 3
5 1
2
4 5
1 3
*/

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