Submission #1057314

#	Time	Username	Problem	Language	Result	Execution time	Memory
1057314		mnbvcxz123	One-Way Streets (CEOI17_oneway)	C++17	100 / 100	46 ms	22468 KiB

oneway

    #include<bits/stdc++.h>
     
    using namespace std;
    int n, m, p, u, v, lead[100005], low[100005], num[100005], d = 0, cnt = 0, ans[100005], timer = 0, q, val[100005];
    vector<pair<int,int>> adj[100005];
    vector<pair<int,int>> adj2[100005], edge;
    stack<int> s;
    bool mark[100005];
    void dfs(int u, int id) {
    	low[u] = num[u] = ++d;
    	s.push(u);
    	for (pair<int, int> W: adj[u]) {
    		int node = W.first;
    		if(W.second == id) continue;
    		if(num[node] != 0) low[u] = min(low[u], num[node]);
    		else {
    			dfs(node, W.second);
    			low[u] = min(low[u], low[node]);
    		}
    	}
    	if(low[u] == num[u]) {
    		cnt++;
    		while(s.top() != u) lead[s.top()] = cnt, s.pop();
    		lead[s.top()] = cnt, s.pop();
    	}
    }
    void cal(int u, int par) {
    	for (pair<int, int> node: adj2[u]) {
    		if(mark[node.first]) continue;
    		mark[node.first] = true;
    		cal(node.first, u);
    		val[u] += val[node.first];
    	}
    }
    void get_ans(int u, int par) {
    	for (pair<int, int> node: adj2[u]) {
    		if(mark[node.first]) continue;
    		mark[node.first] = true;
    		int x, y;
    		x = u, y = node.first;
    		int id = node.second;
    		//cout << "QWFQWF " << x << ' ' << y  << ' ' << id << '\n';
    		if(val[node.first] < 0) {
    			//cout << "EDGE " << x << ' ' << y << ' ' << edge[id].first << ' ' << edge[id].second << '\n';
    			if(lead[edge[id].first] == x && lead[edge[id].second] == y) ans[id+1] = 1;
    			else ans[id+1] = 2;
    		}
    		else if(val[node.first] > 0) {
    			//cout << "EDGE " << x << ' ' << y << ' ' << edge[id].first << ' ' << edge[id].second << '\n';
    			if(lead[edge[id].first] == x && lead[edge[id].second] == y) ans[id+1] = 2;
    			else ans[id+1] = 1;
    		}
    		else ans[id+1] = 0;
    		get_ans(node.first, u);
    	}
    }
    void solve() {
    	cin >> n >> m;
    	for (int i = 1; i <= m; i++) {
    		cin >> u >> v;
    		edge.push_back({u,v});
    		adj[u].push_back({v,i});
    		adj[v].push_back({u,i});
    	}
    	for (int i = 1; i <= n; i++) {
    		if(num[i] == 0) dfs(i, -1);
    	}
    	int idx = 0;
    	for (pair<int, int> i: edge) {
    		if(lead[i.first] != lead[i.second]) adj2[lead[i.first]].push_back({lead[i.second], idx}), adj2[lead[i.second]].push_back({lead[i.first],idx});
    		idx++;
    	}
    	cin >> q;
    	while(q--) {
    		cin >> u >> v;
    		u = lead[u];
    		v = lead[v];
    		val[u]++;
    		val[v]--;
    	}
    	for (int i = 1; i <= cnt; i++) if(!mark[i]) cal(i,-1);
    	memset(mark, 0, sizeof(mark));
    	for (int i = 1; i <= cnt; i++) if(!mark[i]) get_ans(i, -1);
    	for (int i = 1; i <= m; i++) if(ans[i] == 0) cout << 'B'; else if(ans[i] == 1) cout << 'R'; else cout << 'L';
    }
     
    signed main() {
    	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    	if(fopen("input.inp","r")){
    		freopen("input.inp", "r", stdin);
    		freopen("output.out", "w", stdout);
    	}
    	int t = 1;
    	// cin >> t;
    	while(t--) {
    		solve();
    	}
    }

Compilation message (stderr)

oneway.cpp: In function 'int main()':
oneway.cpp:90:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   90 |       freopen("input.inp", "r", stdin);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:91:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   91 |       freopen("output.out", "w", stdout);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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