Submission #1006670

#	Time	Username	Problem	Language	Result	Execution time	Memory
1006670		SulA	One-Way Streets (CEOI17_oneway)	C++17	0 / 100	1 ms	4188 KiB

oneway

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5;
 
vector<int> adj[MAXN+1];
map<pair<int,int>, int> edge;
map<pair<int,int>, char> ans;
int dep[MAXN+1], low[MAXN+1], cntX[MAXN+1], cntY[MAXN+1];
 
void dfs(int v, int p) {
    dep[v] = low[v] = dep[p] + 1;
    for (int u : adj[v]) {
        if (u == p || u == v) continue;
        if (dep[u] == 0) {
            dfs(u, v);
            low[v] = min(low[v], low[u]);
            cntX[v] += cntX[u];
            cntY[v] += cntY[u];
        } else {
            low[v] = min(low[v], dep[u]);
        }
    }
    int node1 = v, node2 = p;
    if (cntX[v] == cntY[v] || dep[v] != low[v] || edge[{v,p}] + edge[{p,v}] != 1) return;
    
    if (edge.find({v, p}) == edge.end()) swap(node1, node2);
    pair<int,int> orient;
    if (cntX[v] > cntY[v]) {
        // edge should go from v -> p
        orient = {v, p};
    } else {
        orient = {p, v};
    }
 
    if (orient == make_pair(node1, node2)) {
        ans[{node1, node2}] = 'R';
    } else {
        ans[{node1, node2}] = 'L';
    }
}
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
 
    int n,m; cin >> n >> m;
    pair<int,int> graph[m];
    for (int i = 0; i < m; i++) {
        int a,b; cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
        edge[{a,b}]++;
        edge[{b, a}]++;
        graph[i] = {a, b};
    }
    int p; cin >> p;
    while (p--) {
        int x,y; cin >> x >> y;
        cntX[x]++, cntY[y]++;
    }
 
    for (int v = 1; v <= n; v++) {
        if (dep[v] == 0) {
            dfs(v,0);
        }
    }
    
    for (auto [a,b] : graph) {
        cout << (!ans.count({a,b}) ? 'B' : ans[{a,b}]);
    }
}

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