Submission #1003573

#	Time	Username	Problem	Language	Result	Execution time	Memory
1003573		ilef	Race (IOI11_race)	C++17	100 / 100	289 ms	33372 KiB

race

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

#define nmax 200020
#define ii pair<int, int>
#define ll long long

int n, k, ans, cnt[1000100], sz[nmax], r[nmax];
vector<ii> adj[nmax];

inline void minimize(int &a, int b)
{
    if(a == -1 || a > b)
        a = b;
}

int dfs(int u, int p = -1)
{
    sz[u] = 1;
    for(auto [C, v]: adj[u]) {
        if(v != p && !r[v]) sz[u] += dfs(v, u);
    }
    return sz[u];
}

int get_centroid(int m, int u, int p = -1)
{
    for(auto [C, v]: adj[u]) {
        if(v != p && !r[v] && 2 * sz[v] > m) return get_centroid(m, v, u);
    }
    return u;
}

void get_cnt(int sum, bool filling, int u, int p = -1, int depth = 1)
{
    if(sum > k) return;
    if(filling)
        minimize(cnt[sum], depth);
    else {
        if(cnt[k - sum] != -1)
            minimize(ans, depth + cnt[k - sum]);
    }
    for(auto [C, v]: adj[u]) {
        if(v != p && !r[v]) get_cnt(sum + C, filling, v, u, depth + 1);
    }
}

void del(int sum, int u, int p = -1)
{
    if(sum > k) return;
    cnt[sum] = -1;
    for(auto [C, v]: adj[u]) {
        if(v != p && !r[v])
            del(sum + C, v, u);
    }
}

void centroid(int u = 0)
{
    u = get_centroid(dfs(u), u);
    r[u] = 1;
    cnt[0] = 0;
    for(auto [C, v]: adj[u]) {
        if(!r[v]) {
            get_cnt(C, false, v);
            get_cnt(C, true, v);
        }
    }
    for(auto [C, v]: adj[u]) {
        if(!r[v]) {
            del(C, v);
        }
    }
    for(auto [C, v]: adj[u]) {
        if(!r[v]) centroid(v);
    }
}

int best_path(int N, int K, int h[][2], int L[])
{
    n = N;
    k = K;
    for(int i = 0, u, v; i < n - 1; ++i) {
        u = h[i][0];
        v = h[i][1];
        adj[u].push_back(ii(L[i], v));
        adj[v].push_back(ii(L[i], u));
    }
    ans = -1;
    memset(cnt, -1, sizeof(cnt));
    centroid();
    return ans;
}

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