Submission #727276

#	Time	Username	Problem	Language	Result	Execution time	Memory
727276		colossal_pepe	Race (IOI11_race)	C++17	21 / 100	3054 ms	20120 KiB

race

#include "race.h"
#include <iostream>
#include <vector>
#include <map>
using namespace std;

int n, k, ans = 1e9;
vector<vector<pair<int, int>>> g;

map<int, int> dfs(int u, int par, int s, int d) {
    map<int, int> ret;
    ret[s] = d;
    for (auto [v, w] : g[u]) {
        if (v == par) continue;
        map<int, int> res = dfs(v, u, s + w, d + 1);
        if (ret.size() > res.size()) swap(ret, res);
        for (auto [sv, dv] : res) {
            int su = k - (sv - 2 * s);
            if (ret.find(su) != ret.end()) ans = min(ans, dv + ret[su] - 2 * d);
        }
        for (auto [sv, dv] : res) {
            if (ret.find(sv) != ret.end()) ret[sv] = min(ret[sv], dv);
            else ret[sv] = dv;
        }
    }
    return ret;
}

int best_path(int N, int K, int H[][2], int L[]) {
    n = N;
    k = K;
    g.resize(n);
    for (int i = 0; i < n - 1; i++) {
        g[H[i][0]].push_back({H[i][1], L[i]});
        g[H[i][1]].push_back({H[i][0], L[i]});
    }
    dfs(0, 0, 0, 0);
    return (ans > n ? -1 : ans);
}

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