Submission #1043959

#	Time	Username	Problem	Language	Result	Execution time	Memory
1043959		GasmaskChan	Race (IOI11_race)	C++17	0 / 100	2 ms	9564 KiB

race

#include <bits/stdc++.h>

using namespace std;

const int MAX = 2e5 + 5;
vector<pair<int, int>> g[MAX];

int k, ans = 1e9;
bitset<MAX> deleted;

struct cal {
    unordered_map<int, int> mp;

    void update(int u, int p, int sum, int depth) {
        if (sum > k) return;
        auto &cur = mp[sum];
        if (cur == 0) cur = depth;
        else cur = min(cur, depth);

        for (auto &[v, w] : g[u]) {
            if (v != p && !deleted[v]) {
                update(v, u, sum + w, depth + 1);
            }
        }
    }

    void add(int u, int p, int sum, int depth) {
        if (sum > k) return;
        auto it = mp.find(k - sum);
        if (it != mp.end()) ans = min(ans, it->second + depth);

        for (auto &[v, w] : g[u]) {
            if (v != p && !deleted[v]) {
                add(v, u, sum + w, depth + 1);
            }
        }
    }

    void lamviec(int u) {
        mp[0] = 0;
        for (auto &[v, w] : g[u]) {
            if (!deleted[v]) {
                add(v, u, w, 1);
                update(v, u, w, 1);
            }
        }
    }
};

int sz[MAX];
void dfs(int u, int p) {
    sz[u] = 1;
    for (auto &[v, w] : g[u]) {
        if (v != p && !deleted[v]) {
            dfs(v, u);
            sz[u] += sz[v];
        }
    }
}

int findcentroid(int u, int p, const int &n) {
    for (auto &[v, w] : g[u]) {
        if (v != p && !deleted[v] && sz[v] * 2 > n) return findcentroid(v, u, n);
    }
    return u;
}

void decompose(int u) {
    dfs(u, 0);
    u = findcentroid(u, 0, sz[u]);
    deleted[u] = true;
    cal tmp; tmp.lamviec(u);

    for (auto &[v, w] : g[u]) {
        if (!deleted[v]) {
            decompose(v);
        }
    }
}

int best_path(int N, int K, int H[][2], int L[]) {
    int n = N;
    k = K;
    for (int u, v, w, i = 0; i < n - 1; i++) {
        u = H[i][0], v = H[i][1], w = L[i];
        ++u, ++v;
        g[u].emplace_back(v, w);
        g[v].emplace_back(u, w);
    }

    decompose(1);

    if (ans == (int)1e18) ans = -1;
    return ans;
}

• Subtask 1: 0 / 9
• Subtask 2: 0 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57