Submission #579990

#	Time	Username	Problem	Language	Result	Execution time	Memory
579990		thezomb1e	One-Way Streets (CEOI17_oneway)	C++17	0 / 100	5 ms	340 KiB

oneway

//thatsramen

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define eb emplace_back
#define pb push_back
#define ft first
#define sd second
#define pi pair<int, int>
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define dbg(...) dbg_out(__VA_ARGS__)

using ll = long long;
using ld = long double;
using namespace std;
using namespace __gnu_pbds;

//Constants
const ll INF = 5 * 1e18;
const int IINF = 2 * 1e9;
const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
const ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const ld PI = 3.14159265359;

//Templates
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) {return os << '(' << p.first << ", " << p.second << ')';}
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) {os << '['; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << ']';}
void dbg_out() {cerr << endl;}
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << H << ' '; dbg_out(T...); }
template<typename T> void mins(T& x, T y) {x = min(x, y);}
template<typename T> void maxs(T& x, T y) {x = max(x, y);}
template<typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T> using omset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;

//order_of_key(k): number of elements strictly less than k
//find_by_order(k): k-th element in the set

void setPrec() {cout << fixed << setprecision(15);}
void unsyncIO() {cin.tie(0)->sync_with_stdio(0);}
void setIn(string s) {freopen(s.c_str(), "r", stdin);}
void setOut(string s) {freopen(s.c_str(), "w", stdout);}
void setIO(string s = "") {
    unsyncIO(); setPrec();
    if(s.size()) setIn(s + ".in"), setOut(s + ".out");
}

// #define TEST_CASES

void solve() {
    int n, m;
    cin >> n >> m;
    vector<vector<pi>> e(n + 5);
    for (int i = 1; i <= m; i++) {
        int u, v; cin >> u >> v;
        e[u].pb({v, i});
        e[v].pb({u, -i});
    }
    vector<bool> vis(n + 5, false);
    vector<char> ans(m + 5, 'B');
    vector<int> dp(n + 5, IINF), dep(n + 5, 0);
    int ed; bool found = false;
    function<void(int, int)> dfs = [&](int f, int p) {
        vis[f] = true;
        if (f == ed) found = true;
        dp[f] = dep[f];
        for (pi to : e[f]) {
            if (vis[to.ft] && to.ft != p) {
                mins(dp[f], dep[to.ft]);
            }
            if (!vis[to.ft]) {
                dep[to.ft] = dep[f] + 1;
                bool prev = found;
                dfs(to.ft, f);
                //dbg("node:", f, "to:", to.ft, dp[to.ft]);
                if (dp[to.ft] > dep[f] && !prev && found) {
                    // bridge
                    if (to.sd > 0) {
                        ans[to.sd] = 'R';
                    } else {
                        ans[-to.sd] = 'L';
                    }
                }
                mins(dp[f], dp[to.ft]);
            }
        }
    };
    int q; cin >> q;
    vector<pi> need(q);
    for (int i = 0; i < q; i++) {
        cin >> need[i].ft >> need[i].sd;
    }
    for (pi x : need) {
        fill(all(vis), false);
        fill(all(dp), IINF);
        fill(all(dep), 0);
        found = false;
        ed = x.sd, dfs(x.ft, -1);
    }
    for (int i = 1; i <= m; i++) {
        cout << ans[i];
    }
}

int main() {
    setIO();

    int tt = 1;
    #ifdef TEST_CASES
        cin >> tt;
    #endif

    while (tt--)
        solve();

    return 0;
}

Compilation message (stderr)

oneway.cpp: In function 'void setIn(std::string)':
oneway.cpp:44:30: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   44 | void setIn(string s) {freopen(s.c_str(), "r", stdin);}
      |                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp: In function 'void setOut(std::string)':
oneway.cpp:45:31: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   45 | void setOut(string s) {freopen(s.c_str(), "w", stdout);}
      |                        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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