Submission #832072

#	Time	Username	Problem	Language	Result	Execution time	Memory
832072		skittles1412	Towns (IOI15_towns)	C++17	90 / 100	14 ms	876 KiB

towns

#include "bits/extc++.h"

using namespace std;

template <typename T, typename... U>
void dbgh(const T& t, const U&... u) {
    cerr << t;
    ((cerr << " | " << u), ...);
    cerr << endl;
}

#ifdef DEBUG
#define dbg(...)                                              \
    cerr << "L" << __LINE__ << " [" << #__VA_ARGS__ << "]: "; \
    dbgh(__VA_ARGS__)
#else
#define dbg(...)
#define cerr   \
    if (false) \
    cerr
#endif

#define endl "\n"
#define long int64_t
#define sz(x) int(std::size(x))

struct DSU {
    vector<int> p;

    DSU(int n) : p(n, -1) {}

    int find(int u) {
        return p[u] < 0 ? u : (p[u] = find(p[u]));
    }

    int size(int u) {
        return -p[find(u)];
    }

    bool merge(int u, int v) {
        u = find(u);
        v = find(v);
        if (u == v) {
            return false;
        }
        if (p[u] < p[v]) {
            swap(u, v);
        }
        p[v] += p[u];
        p[u] = v;
        return true;
    }
};

int getDistance(int i, int j);

struct G {
    map<pair<int, int>, int> cache;

    int query(int u, int v) {
        if (u == v) {
            return 0;
        }
        if (u > v) {
            swap(u, v);
        }
        auto [it, inserted] = cache.insert({{u, v}, -1});
        if (!inserted) {
            return it->second;
        }
        return it->second = getDistance(u, v);
    }
} G;

int hubDistance(int n, int tc_id) {
    G = {};

    auto farthest = [&](int u) -> int {
        pair<int, int> ans {-1, 0};
        for (int i = 0; i < n; i++) {
            ans = max(ans, {G.query(u, i), i});
        }
        return ans.second;
    };

    int u1 = farthest(0), u2 = farthest(u1), diam = G.query(u1, u2);

    int u_hori[n], u_down[n];
    for (int i : {0}) {
        int d1 = G.query(u1, i), d2 = G.query(u2, i);

        u_down[i] = (d1 + d2 - diam) / 2;
        u_hori[i] = d1 - u_down[i];
    }
    for (int i = 1; i < n; i++) {
        int d1 = G.query(u1, i), d0 = G.query(0, i);

        int common = (d1 + d0 - G.query(0, u1)) / 2, l0 = d0 - common, l1 = d1 - common;
        if (l0 <= u_down[0]) {
            u_hori[i] = u_hori[0];
            u_down[i] = common + l1 - u_hori[0];
        } else if (l1 < u_hori[0]) {
            u_hori[i] = l1;
            u_down[i] = common;
        } else {
            assert(l1 > u_hori[0]);
            u_hori[i] = d1;
            u_down[i] = 0;
        }
    }

    int ans = 1e9;

    for (int i = 0; i < n; i++) {
        ans = min(ans, max(u_hori[i], diam - u_hori[i]));
    }

    vector<int> cands;
    {
        map<int, int> mp;
        for (auto& a : u_hori) {
            mp[a]++;
        }

        bool ok = false;
        int cl = 0;
        for (auto& [k, v] : mp) {
            if (max(k, diam - k) > ans) {
                cl += v;
                continue;
            }

            int cm = v, cr = n - cl - cm;
            dbg(cl, cm, cr);
            if (max({cl, cm, cr}) <= n / 2) {
                ok = true;
            }
            if (max(cl, cr) <= n / 2) {
                cands.push_back(k);
            }

            cl += v;
        }

        if (ok) {
            return ans;
        }
    }

    if (!sz(cands)) {
        return -ans;
    }
    assert(sz(cands) == 1);

    if (tc_id > 2 && tc_id != 4) {
        vector<int> nodes;
        for (int i = 0; i < n; i++) {
            if (u_hori[i] == cands[0]) {
                nodes.push_back(i);
            }
        }

        auto same_child = [&](int u, int v) -> bool {
            return G.query(u, v) != u_down[u] + u_down[v];
        };

        vector<int> u_same, u_diff;
        vector<pair<vector<int>, vector<int>>> segs;

        for (auto& a : nodes) {
            if (!sz(u_same)) {
                u_same.push_back(a);
            } else {
                if (same_child(u_same[0], a)) {
                    u_same.push_back(a);
                } else {
                    u_diff.push_back(a);
                }
            }

            if (sz(u_same) == sz(u_diff)) {
                segs.emplace_back(u_same, u_diff);
                u_same.clear();
                u_diff.clear();
            }
        }

        if (!sz(u_same)) {
            return ans;
        }

        int ccnt = sz(u_same);
        for (auto& [s, d] : segs) {
            if (same_child(s[0], u_same[0])) {
                ccnt += sz(d);
            }

            for (auto& a : d) {
                if (same_child(a, u_same[0])) {
                    ccnt++;
                }
            }
        }

        if (ccnt <= n / 2) {
            return ans;
        }

        return -ans;
    }

    return -ans;
}

• Subtask 1: 13 / 13
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 0 / 10
• Subtask 5: 13 / 13
• Subtask 6: 39 / 39