Submission #886214

#	Time	Username	Problem	Language	Result	Execution time	Memory
886214		Zero_OP	One-Way Streets (CEOI17_oneway)	C++14	0 / 100	1 ms	6748 KiB

oneway

#include<bits/stdc++.h>

using namespace std;

#define range(v) begin(v), end(v)
#define compact(v) v.erase(unique(range(v)), end(v))

template<class T> bool minimize(T& a, T b){
    if(a > b) return a = b, true;
    return false;
}

template<class T> bool maximize(T& a, T b){
    if(a < b) return a = b, true;
    return false;
}

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;

const int N = 1e5 + 5;
const int Left = 0;
const int Right = 1;
const int Both = 2;
const char c[] = {'L', 'R', 'B'};

int n, m, low[N], num[N], id[N], dp[N], ans[N], timerDFS, timerSCC;
pair<int, int> e[N], E[N];
vector<pair<int, int>> g[N], G[N];
stack<int> stck;
bitset<N> vst;

void dfsTarjan(int u, int preID){
    low[u] = num[u] = ++timerDFS;
    stck.push(u);
    for(auto [id, dir] : g[u]) if(id != preID){
        int v = e[id].first ^ e[id].second ^ u;
        if(num[v]) {
            minimize(low[u], num[v]);
        }
        else{
            dfsTarjan(v, id);
            minimize(low[u], low[v]);
        }
    }
    if(low[u] == num[u]){
        ++timerSCC;
        do{
            int v = stck.top(); stck.pop();
            id[v] = timerSCC;
            low[u] = num[u] = N;
        } while(!id[u]);
    }
}

void dfsSolve(int u, int preID){
    vst[u] = true;

    for(auto [id, target] : G[u]) if(preID != id){
        int v = E[id].first ^ E[id].second ^ u;
        dfsSolve(v, id);
        dp[u] += dp[v];

        if(dp[v] == 0) ans[id] = Both;
        else if(dp[v] < 0) ans[id] = (target == 0 ? Right : Left);
        else ans[id] = (target == 0 ? Left : Right);
    }
}

void Zero_OP(){
    cin >> n >> m;
    for(int i = 1; i <= m; ++i){
        int u, v;
        cin >> u >> v;
        g[u].push_back({i, 0});
        g[v].push_back({i, 1});
        e[i] = {u, v};
    }

    for(int i = 1; i <= n; ++i){
        if(!num[i]) dfsTarjan(1, -1);
    }
    for(int i = 1; i <= m; ++i){
        int u, v;
        tie(u, v) = e[i];
        E[i] = {id[u], id[v]};
        if(id[u] != id[v]){
            G[id[u]].push_back({i, 0});
            G[id[v]].push_back({i, 1});
        }
        else ans[i] = Both;
    }

    int q; cin >> q;
    for(int i = 1; i <= q; ++i){
        int u, v;
        cin >> u >> v;
        u = id[u], v = id[v];
        ++dp[u];
        --dp[v];
    }

    for(int i = 1; i <= timerSCC; ++i){
        if(!vst[i]){
            dfsSolve(i, -1);
        }
    }

    for(int i = 1; i <= m; ++i){
        cout << c[ans[i]];
    }
}

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

    #define task "antuvu"
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }

    Zero_OP();

    return 0;
}

Compilation message (stderr)

oneway.cpp: In function 'void dfsTarjan(int, int)':
oneway.cpp:37:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   37 |     for(auto [id, dir] : g[u]) if(id != preID){
      |              ^
oneway.cpp: In function 'void dfsSolve(int, int)':
oneway.cpp:60:14: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   60 |     for(auto [id, target] : G[u]) if(preID != id){
      |              ^
oneway.cpp: In function 'int main()':
oneway.cpp:121:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  121 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:122:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  122 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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