Submission #748234

#	Time	Username	Problem	Language	Result	Execution time	Memory
748234		Desh03	Race (IOI11_race)	C++17	0 / 100	1 ms	212 KiB

race

#include "race.h"
#include <bits/stdc++.h>
using namespace std;

int k, ans = 1e9, mxd;
vector<vector<pair<int, int>>> g;
vector<int> sz, dep;
vector<multiset<int>> dp;
vector<bool> centroid;

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

int findcentroid(int u, int p, int mx) {
    for (auto [v, w] : g[u])
        if (v ^ p && !centroid[v] && sz[v] * 2 > mx)
            return findcentroid(v, u, mx);
    return u;
}

void calcdep(int u, int p, int d) {
    dep[u] = d;
    for (auto [v, w] : g[u])
        if (v ^ p && !centroid[v])
            calcdep(v, u, d + 1);
}

void addmx(int u, int p, int length) {
    if (length > k) return;
    dp[length].insert(dep[u]);
    for (auto [v, w] : g[u])
        if (v ^ p && !centroid[v])
            addmx(v, u, length + w);
}

void calcmx(int u, int p, int length) {
    if (length > k) return;
    if (dp[k - length].size())
        ans = min(ans, dep[u] + *dp[k - length].begin());
    mxd = max(mxd, dep[u]);
    for (auto [v, w] : g[u])
        if (v ^ p && !centroid[v])
            calcmx(v, u, length + w);
}

void decompose(int u) {
    calc(u, u);
    int x = findcentroid(u, u, sz[u]);
    calcdep(x, x, 0);
    centroid[x] = 1, mxd = 0;
    for (auto [v, w] : g[x]) {
        if (!centroid[v]) {
            calcmx(v, x, w);
            addmx(v, x, w);
        }
    }
    if (dp[k].size()) ans = min(ans, *dp[k].begin());
    for (int i = 1; i <= mxd; i++) dp[i].clear();
    for (auto [v, w] : g[x]) {
        if (!centroid[v])
            decompose(v);
    }
}

int best_path(int n, int k_, int h[][2], int l[]) {
    k = k_;
    g = vector<vector<pair<int, int>>> (n), centroid = vector<bool> (n), dep = vector<int> (n), dp = vector<multiset<int>>(k + 1), sz = dep;
    for (int i = 0; i < n - 1; i++) {
        int u = h[i][0], v = h[i][1], w = l[i];
        g[u].push_back({v, w});
        g[v].push_back({u, w});
    }
    dp[0].insert(0);
    decompose(0);
    return ans == 1e9 ? -1 : ans;
}

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