Submission #1118837

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118837		gdragon	One-Way Streets (CEOI17_oneway)	C++17	60 / 100	3054 ms	20812 KiB

oneway

#include <bits/stdc++.h>
using namespace std;
#define TASK "long"
#define fi first
#define se second
#define ll long long
#define pb push_back
#define ALL(x) (x).begin(), (x).end()
#define GETBIT(mask, i) ((mask) >> (i) & 1)
#define MASK(i) ((1LL) << (i))
#define SZ(x) ((int)(x).size())
#define mp make_pair
#define CNTBIT(mask) __builtin_popcount(mask)
template<class X, class Y> bool maximize(X &x, Y y){ if (x < y) {x = y; return true;} return false;};
template<class X, class Y> bool minimize(X &x, Y y){ if (x > y) {x = y; return true;} return false;};
typedef pair<int, int> ii;
const int N = 1e5 + 5;
const int inf = 1e9 + 7;
const long long INF = (long long)1e18 + 7;
const int mod = 1e9 + 7;
struct Edge {
    int u, v;
    bool isBridge, used;
    Edge(int _u = 0, int _v = 0) {
        u = _u; v = _v;
        isBridge = used = 0;
    }
} e[N];
int n, m, q;
int low[N], num[N];
vector<int> adj[N];
vector<ii> newAdj[N];
void read() {
    cin >> n >> m;
    for(int i = 1; i <= m; i++) {
        int u, v; cin >> u >> v;
        e[i] = Edge(u, v);
        adj[u].push_back(i);
        adj[v].push_back(i);
    }
}
int timer = 0, cycle = 0;
stack<int> st;
int id[N];
void tarjan(int u) {
    low[u] = num[u] = ++timer;
    st.push(u);
    for(int i: adj[u]) if (!e[i].used) {
        e[i].used = 1;
        int v = e[i].u ^ e[i].v ^ u;
        if (num[v]) low[u] = min(low[u], num[v]);
        else {
            tarjan(v);
            low[u] = min(low[u], low[v]);
        }
        if (low[v] > num[u]) {
            // cerr << "BRIDGE: " << e[i].u << ' ' << e[i].v << endl;
            e[i].isBridge = 1;
        }
    }
    if (low[u] == num[u]) {
        ++cycle;
        // cerr << cycle << endl;
        while(true) {
            int v = st.top(); st.pop();
            // cerr << v << ' ';
            low[v] = num[v] = inf;
            id[v] = cycle;
            if (v == u) break;
        }
        // cerr << endl;
    }
}
int tin[N], tout[N], high[N];
ii par[N];
bool isChild(int u, int p) {
    return tin[u] >= tin[p] && tin[u] <= tout[p];
}
int jump[N];
void dfs(int u, int p) {
    // cerr << u << endl;
    tin[u] = ++timer;
    jump[u] = u;
    for(auto [v, i]: newAdj[u]) if (v != p) {
        par[v] = {u, i};
        high[v] = high[u] + 1;
        dfs(v, u);
    } 
    tout[u] = timer;
}
int ans[N];
int change[N];
vector<int> node;
void solve() {
    for(int i = 1; i <= n; i++) if (!num[i]) {
        tarjan(i);
        // assert(i == 1);
    }
    for(int i = 1; i <= m; i++) if (e[i].isBridge) {
        int u = id[e[i].u], v = id[e[i].v];
        newAdj[u].push_back({v, i});
        newAdj[v].push_back({u, i});
    }
    timer = 0;
    for(int i = 1; i <= cycle; i++) if (!tin[i]) dfs(i, -1);
    cin >> q;
    while(q--) {
        int u, v; cin >> u >> v;
        // cerr << id[u] << ' ' << id[v] << endl;
        if (id[u] == id[v]) continue;
        u = id[u]; v = id[v];
        int tmp = u;
        // cerr << jump[u] << ' ' << v << ' ' << isChild(jump[u], v) << endl;
        while(!isChild(v, u)) {
            int i = par[u].se;
            // u = par[u].fi;
            ans[i] = 1;
            // node.push_back(u);
            u = par[u].fi;
        }
        // for(int x: node) jump[x] = u;
        node.clear();
        u = tmp;
        while(!isChild(u, v)) {
            int i = par[v].se;
            ans[i] = 2;
            // cerr << v << ' ' << e[i].u << ' ' << e[i].v << endl;
            // node.push_back(v);
            v = par[v].fi;
        }
        // for(int x: node) jump[x] = v;
        node.clear();
    }
    for(int i = 1; i <= m; i++) {
        // cout << e[i].u << ' ' << e[i].v << ' ';
        if (e[i].isBridge) {
            if (ans[i] != 0) {
                int u = e[i].u, v = e[i].v;
                if (high[id[u]] < high[id[v]]) {
                    assert(isChild(id[v], id[u]));
                    if (ans[i] == 2) cout << 'R';
                    else cout << 'L';
                }
                else {
                    assert(isChild(id[u], id[v]));
                    if (ans[i] == 2) cout << 'L';
                    else cout << 'R';
                }
            }
            else cout << 'B';
            // cout << endl;
            continue;
        }
        else cout << 'B';
        // cout << endl;
    }
}
signed main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if (fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }
    int test = 1;
    // cin >> test;
    while(test--) {
        read();
        solve();
    }
    return 0;
}

// rmq - rmq2d
// hash
// fw - fw2d
// segtree

Compilation message (stderr)

oneway.cpp: In function 'int main()':
oneway.cpp:161:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  161 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
oneway.cpp:162:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  162 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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