Submission #379294

#	Time	Username	Problem	Language	Result	Execution time	Memory
379294		justiny7	Race (IOI11_race)	C++17	0 / 100	4 ms	5100 KiB

race

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

const int mxN=2e5+1, mxK=1e6+1, INF=1e9;
int ans=INF, sz[mxN], mn[mxN];
vector<pair<int, int>> adj[mxN];
bool vis[mxN];

int dfs_sz(int v, int p=-1) {
    sz[v]=1;
    for (auto [u, d]:adj[v])
        if (!vis[u] && u^p)
            sz[v]+=dfs_sz(u, v);
    return sz[v];
}
int dfs_centroid(int tot, int v, int p=-1) {
    for (auto [u, d]:adj[v])
        if (!vis[u] && u^p && sz[u]*2>tot)
            return dfs_centroid(tot, u, v);
    return v;
}
void dfs(int k, int v, int p=-1, int dep=0, int len=0) {
    mn[len]=min(mn[len], dep);
    for (auto [u, d]:adj[v])
        if (!vis[u] && u^p && len+d<=k)
            dfs(k, u, v, dep+1, len+d);
}
void decomp(int k, int x=0) {
    int v=dfs_centroid(dfs_sz(x), x);
    vis[v]=1;
    fill(mn+1, mn+k+1, INF);
    dfs(k, v);
    for (int i=0; i<=k/2; ++i)
        ans=min(ans, mn[i]+mn[k-i]);
    for (auto [u, d]:adj[v])
        if (!vis[u])
            decomp(k, u);
}

int best_path(int N, int K, int H[][2], int L[]) {
    for (int i=0; i<N; ++i)
        adj[i].clear();
    for (int i=0; i<N-1; ++i) {
        adj[H[i][0]].emplace_back(H[i][1], L[i]);
        adj[H[i][1]].emplace_back(H[i][0], L[i]);
    }
    decomp(K);
    return (ans==INF?-1:ans);
}

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