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Submission #151735

# Submission time Handle Problem Language Result Execution time Memory
151735 2019-09-04T12:39:14 Z forestryks One-Way Streets (CEOI17_oneway) C++14
100 / 100
 273 ms 30320 KB 
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using ld = long double;
using pii = pair<int, int>;
#define rep(i, n) for (int (i) = 0; (i) < (n); ++(i))
#define all(x) (x).begin(), (x).end()
#define FAST_IO ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);

struct edge {
    int u, v, id;
};

const int MAXN = 1e5 + 5;
int n, m;
vector<edge> e;
vector<int> g[MAXN];
int tt = 0;
int tin[MAXN];
int fup[MAXN];
bool used[MAXN];

int dsu[MAXN];
int sz[MAXN];

void init() {
    rep(i, n) {
        dsu[i] = i;
        sz[i] = 1;
    }
}

int get(int v) {
    if (dsu[v] == v) return v;
    return (dsu[v] = get(dsu[v]));
}

void merge(int u, int v) {
    u = get(u);
    v = get(v);
    if (u == v) return;
    if (sz[u] < sz[v]) swap(u, v);
    dsu[v] = u;
    sz[u] += sz[v];
}

void dfs(int v, int p) {
    tin[v] = fup[v] = tt++;
    used[v] = true;
    for (auto to : g[v]) {
        if (to == p) {
            p = -1;
            continue;
        }
        if (used[to]) {
            fup[v] = min(fup[v], tin[to]);
        } else {
            dfs(to, v);
            if (fup[to] > tin[v]) {
                // bridge
                // cout << v << ' ' << to << endl;
            } else {
                fup[v] = min(fup[v], fup[to]);
                merge(v, to);
            }
        }
    }
}

int p[MAXN];
int h[MAXN];
int tout[MAXN];
int up[MAXN][20];

void pre(int v) {
    used[v] = true;
    if (p[v] == -1) up[v][0] = v;
    else up[v][0] = p[v];
    for (int i = 1; i < 20; ++i) {
        up[v][i] = up[up[v][i - 1]][i - 1];
    }

    tin[v] = tt++;
    for (auto to : g[v]) {
        g[to].erase(find(all(g[to]), v));
        p[to] = v;
        h[to] = h[v] + 1;
        pre(to);
    }
    tout[v] = tt++;
}

int lca(int u, int v) {
    if (tin[u] <= tin[v] && tin[v] < tout[u]) return u;
    for (int i = 19; i >= 0; --i) {
        if (!(tin[up[u][i]] <= tin[v] && tin[v] < tout[up[u][i]])) {
            u = up[u][i];
        }
    }
    return p[u];
}

int eup[MAXN];
int edown[MAXN];

void post(int v) {
    used[v] = true;
    for (auto to : g[v]) {
        post(to);
        eup[v] = max(eup[v], eup[to] - 1);
        edown[v] = max(edown[v], edown[to] - 1);
    }
}

int main() {
    FAST_IO;
    cin >> n >> m;
    rep(i, m) {
        int u, v;
        cin >> u >> v;
        u--; v--;
        g[u].push_back(v);
        g[v].push_back(u);
        e.push_back({u, v, i});
    }

    init();
    rep(i, n) {
        if (!used[i]) {
            dfs(i, -1);
        }
    }

    rep(i, n) {
        g[i].clear();
    }

    map<int, int> cc;

    rep(i, n) {
        dsu[i] = get(i);
    }

    rep(i, n) {
        if (cc.find(dsu[i]) == cc.end()) {
            int id = cc.size();
            cc[dsu[i]] = id;
        }
        dsu[i] = cc[dsu[i]];
    }

    // rep(i, n) {
    //     cout << dsu[i] << ' ';
    // }
    // cout << endl;
    // return 0;

    rep(i, m) {
        int &u = e[i].u, &v = e[i].v;
        u = dsu[u]; v = dsu[v];
        // cout << u << ' ' << v << endl;
        if (u == v) continue;
        g[u].push_back(v);
        g[v].push_back(u);
    }

    tt = 0;
    p[0] = -1;
    fill(used, used + cc.size(), false);
    vector<int> roots;
    rep(i, cc.size()) {
        if (!used[i]) {
            pre(i);
            roots.push_back(i);
        }
    }
    // pre(0);

    // return 0;

    int k;
    cin >> k;
    rep(i, k) {
        int u, v;
        cin >> u >> v;
        u--; v--;
        u = dsu[u];
        v = dsu[v];
        if (u == v) continue;

        int lc = lca(u, v);

        if (u != lc) {
            eup[u] = max(eup[u], h[u] - h[lc]);
        }
        if (v != lc) {
            edown[v] = max(edown[v], h[v] - h[lc]);
        }
    }

    for (auto v : roots) {
        post(v);
    }

    rep(i, m) {
        int u = e[i].u, v = e[i].v;
        if (u == v) {
            cout << 'B';
            continue;
        }
        bool sw = false;
        if (p[v] == u) {
            sw = true;
            swap(u, v);
        }

        // p[u] == v

        if (!edown[u] && !eup[u]) {
            cout << 'B';
            continue;
        }

        if (edown[u]) {
            sw ^= 1;
        }

        cout << "RL"[sw];
    }
    cout << endl;
}

Compilation message

oneway.cpp: In function 'int main()':
oneway.cpp:7:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i, n) for (int (i) = 0; (i) < (n); ++(i))
                                     ~~~~^~~~~
oneway.cpp:172:5: note: in expansion of macro 'rep'
     rep(i, cc.size()) {
     ^~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 2680 KB Output is correct
2 Correct 4 ms 2680 KB Output is correct
3 Correct 5 ms 2808 KB Output is correct
4 Correct 5 ms 2936 KB Output is correct
5 Correct 5 ms 2936 KB Output is correct
6 Correct 4 ms 2808 KB Output is correct
7 Correct 5 ms 2936 KB Output is correct
8 Correct 5 ms 2936 KB Output is correct
9 Correct 5 ms 2812 KB Output is correct
10 Correct 5 ms 2808 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 2680 KB Output is correct
2 Correct 4 ms 2680 KB Output is correct
3 Correct 5 ms 2808 KB Output is correct
4 Correct 5 ms 2936 KB Output is correct
5 Correct 5 ms 2936 KB Output is correct
6 Correct 4 ms 2808 KB Output is correct
7 Correct 5 ms 2936 KB Output is correct
8 Correct 5 ms 2936 KB Output is correct
9 Correct 5 ms 2812 KB Output is correct
10 Correct 5 ms 2808 KB Output is correct
11 Correct 53 ms 8104 KB Output is correct
12 Correct 62 ms 9228 KB Output is correct
13 Correct 72 ms 11132 KB Output is correct
14 Correct 94 ms 15528 KB Output is correct
15 Correct 114 ms 17452 KB Output is correct
16 Correct 179 ms 24532 KB Output is correct
17 Correct 185 ms 26064 KB Output is correct
18 Correct 188 ms 24488 KB Output is correct
19 Correct 187 ms 27184 KB Output is correct
20 Correct 61 ms 9132 KB Output is correct
21 Correct 65 ms 9084 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 2680 KB Output is correct
2 Correct 4 ms 2680 KB Output is correct
3 Correct 5 ms 2808 KB Output is correct
4 Correct 5 ms 2936 KB Output is correct
5 Correct 5 ms 2936 KB Output is correct
6 Correct 4 ms 2808 KB Output is correct
7 Correct 5 ms 2936 KB Output is correct
8 Correct 5 ms 2936 KB Output is correct
9 Correct 5 ms 2812 KB Output is correct
10 Correct 5 ms 2808 KB Output is correct
11 Correct 53 ms 8104 KB Output is correct
12 Correct 62 ms 9228 KB Output is correct
13 Correct 72 ms 11132 KB Output is correct
14 Correct 94 ms 15528 KB Output is correct
15 Correct 114 ms 17452 KB Output is correct
16 Correct 179 ms 24532 KB Output is correct
17 Correct 185 ms 26064 KB Output is correct
18 Correct 188 ms 24488 KB Output is correct
19 Correct 187 ms 27184 KB Output is correct
20 Correct 61 ms 9132 KB Output is correct
21 Correct 65 ms 9084 KB Output is correct
22 Correct 273 ms 27348 KB Output is correct
23 Correct 249 ms 25672 KB Output is correct
24 Correct 243 ms 25908 KB Output is correct
25 Correct 257 ms 30320 KB Output is correct
26 Correct 271 ms 26920 KB Output is correct
27 Correct 251 ms 25792 KB Output is correct
28 Correct 44 ms 6188 KB Output is correct
29 Correct 89 ms 9912 KB Output is correct
30 Correct 89 ms 10028 KB Output is correct
31 Correct 84 ms 10380 KB Output is correct
32 Correct 140 ms 16860 KB Output is correct