Submission #321744

#	Time	Username	Problem	Language	Result	Execution time	Memory
321744		Karen124	One-Way Streets (CEOI17_oneway)	C++14	0 / 100	5 ms	7404 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 = 30;
const ll MOD = 1e9 + 7;
const ll INF = 1e9 + 10;
struct Edge{
    int u, v;
} e[N];
int n, m, p, h[N], mn[N], pr[N], sz[N];
vector < pair <int, int> > adj[N];
vector <int>  E;
bool mrk[N], is[N], rev[N];
set <int> Q[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 && h[u] < h[v]){
            mn[v] = min(mn[v], h[u]);   
        }
    }
    if(mn[v] == h[v]){
        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];
    if (Q[v].size() < Q[u].size()) swap(Q[v], Q[u]);
    while (Q[u].size()){
        auto it_u = Q[u].begin();
        auto it_v = Q[v].lower_bound(-(*it_u));
        if (it_v != Q[v].end() && abs(*it_u) == abs(*it_v)){
            Q[u].erase(it_u); Q[v].erase(it_v);
            continue;
        }
        Q[v].insert(*it_u);
        Q[u].erase(it_u);
    }
    return;
}
void _union(int u, int v, int id){
    u = find(u), v = find(v);
    if (u == v) return;
    bool f = 0;
    if (Q[v].size() < Q[u].size()){
        f = 1;
        swap(Q[u], Q[v]);
    }
    while (Q[u].size()){
        auto it_u = Q[u].begin();
        auto it_v = Q[v].lower_bound(-(*it_u));
        if (it_v != Q[v].end() && abs(*it_u) == abs(*it_v)){
            rev[id] = (((0 < (*it_u)) && (f == 1)) || ((*it_u) < 0) && (f == 0));
            Q[u].erase(it_u); Q[v].erase(it_v);
            continue;
        }
        Q[v].insert(*it_u);
        Q[u].erase(it_u);
    }
    if (sz[v] < sz[u]) swap(u, v);
    pr[u] = v;
    sz[v] += sz[u];
    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++){
        int a, b;
        cin >> a >> b;
        Q[a].insert(i);
        Q[b].insert(-i);
    }
    prepare();
    for (int i = 1; i <= m; i++){
        if (!is[i]){
            merge(e[i].u, e[i].v);
        }
    }
    for (int i : E){
        _union(e[i].u, e[i].v, i);
    }
    for (int i = 1; i <= m; i++){
        if (!is[i]) cout << "B";
        else if (rev[i]) cout << "L";
        else cout << "R";
    }
    cout << '\n';
    return 0;
}
/*
5 6
1 2
1 2
4 3
2 3
1 3
5 1
2
4 5
1 3
*/

Compilation message (stderr)

oneway.cpp: In function 'void _union(int, int, int)':
oneway.cpp:84:69: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   84 |             rev[id] = (((0 < (*it_u)) && (f == 1)) || ((*it_u) < 0) && (f == 0));
      |                                                       ~~~~~~~~~~~~~~^~~~~~~~~~~

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