Submission #461180

#	Time	Username	Problem	Language	Result	Execution time	Memory
461180		KazamaHoang	Race (IOI11_race)	C++14	0 / 100	5 ms	8908 KiB

race

#include <bits/stdc++.h>
#define F first
#define S second
#define eb emplace_back
#define bit(x, i) (((x) >> (i)) & 1)

using namespace std;
using ll = long long;

const int inf = 1061109567;
const ll INF = 4557430888798830399;
const int MOD = 998244353;

int n, lenRace;
vector <pair <int, int>> adj[200005];
int subtree_size[200005];
int minDepth[1000005];
bool vis[200005];
int res = inf;

int dfs(int u, int par) {
    int &ret = subtree_size[u];
    ret = 1;
    for (auto pii : adj[u]) {
        int v = pii.F;
        if (v != par && !vis[v])
            ret += dfs(v, u);
    }
    return ret;
}

int find_centroid(int u, int par, int sz) {
    for (auto pii : adj[u]) {
        int v = pii.F;
        if (v != par && !vis[v] && subtree_size[v] * 2 > sz)
            return find_centroid(v, u, sz);
    }
    return u;
}

void calc(int u, int par, int sign, int depth, int len) {
    if (len > lenRace)
        return;
    if (sign == 0)
        res = min(res, depth + minDepth[lenRace-len]);
    else if (sign == 1)
        minDepth[len] = min(minDepth[len], depth);
    else
        minDepth[len] = inf;
    for (auto pii : adj[u]) {
        int v = pii.F;
        int w = pii.S;
        if (!vis[v] && v != par)
            calc(v, u, sign, depth + 1, len + w);
    }
}

void process(int u) {
    int centroid = find_centroid(u, -1, dfs(u, -1));
    vis[centroid] = true;

    for (auto pii : adj[centroid]) {
        int v = pii.F, w = pii.S;
        if (vis[v])
            continue;
        calc(v, centroid, 0, 1, w);
        calc(v, centroid, 1, 1, w);
    }
    for (auto pii : adj[centroid]) {
        int v = pii.F;
        int w = pii.S;
        if (vis[v])
            continue;
        calc(v, centroid, -1, 1, w);
    }

    for (auto pii : adj[centroid]) {
        int v = pii.F;
        if (vis[v])
            continue;
        process(v);
    }
}

int best_path(int N, int K, int h[][2], int L[]) {
    n = N;
    lenRace = K;
    for (int i = 1; i < n; ++ i) {
        int u = h[i][0] + 1;
        int v = h[i][1] + 1;
        adj[u].eb(v, L[i]);
        adj[v].eb(u, L[i]);
    }
    for (int i = 1; i <= 1e6; ++ i)
        minDepth[i] = inf;
    process(1);
    if (res == inf)
        res = -1;
    return res;
}

//int32_t main(void) {
//    cin.tie(0)->sync_with_stdio(0);
//    if (fopen(".in", "r")) {
//        freopen(".in", "r", stdin);
//        freopen(".out", "w", stdout);
//    }
//    cin >> n >> lenRace;
//    for (int i = 1; i < n; ++ i) {
//        int u, v, w; cin >> u >> v >> w;
//        ++ u, ++ v;
//        adj[u].eb(v, w);
//        adj[v].eb(u, w);
//    }
//    for (int i = 1; i <= 1e6; ++ i)
//        minDepth[i] = inf;
//    process(1);
//    if (res == inf)
//        res = -1;
//    cout << res;
//    return 0;
//}

// Written by Kazama Hoang ^^

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