Submission #104359

#	Time	Username	Problem	Language	Result	Execution time	Memory
104359		nvmdava	Race (IOI11_race)	C++17	100 / 100	730 ms	30968 KiB

race

#include "race.h"
#include <bits/stdc++.h>
#define N 200005
#define pb push_back
#define ff first
#define ss second
#define pii pair<int, int>
using namespace std;
bool blocked[N];
int n, s;

vector<pii> adj[N];
int sz[N];
int sumsz;
int len[5 * N];
int get_size(int v, int p){
    sz[v] = 1;
    for(auto& c : adj[v]){
        if(c.ff == p || blocked[c.ff])
            continue;
        sz[v] += get_size(c.ff, v);
    }
    return sz[v];
}

int get_centroid(int v, int p){
    for(auto& c : adj[v]){
        if(c.ff == p || blocked[c.ff])
            continue;
        if(sz[c.ff] >= sumsz / 2)
            return get_centroid(c.ff, v);
    }
    return v;
}
int ans = N;
queue<pii> q;
queue<int> lol;
void dfs(int v, int p, int l, int cnt){
    if(s >= l)ans = min(ans, len[s - l] + cnt);
    else return;
    q.push({l, cnt});
    lol.push(l);
    cnt++;
    for(auto& c : adj[v]){
        if(c.ff == p || blocked[c.ff])
            continue;
        dfs(c.ff, v, l + c.ss, cnt);
    }
    if(p == -1){
        while(!q.empty()){
            len[q.front().ff] = min(len[q.front().ff], q.front().ss);
            q.pop();
        }
    }
}

void decomp(int v){
    sumsz = get_size(v, -1);
    v = get_centroid(v, -1);
    blocked[v] = 1;
    len[0] = 0;
    for(auto &c : adj[v]){
        if(blocked[c.ff])
            continue;
        dfs(c.ff, -1, c.ss, 1);
    }
    while(!lol.empty()){
        len[lol.front()] = 0x3f3f3f3f;
        lol.pop();
    }
    for(auto &c : adj[v]){
        if(blocked[c.ff])
            continue;
        decomp(c.ff);
    }
}


int best_path(int n, int s, int h[][2], int l[]){
    ::n = n;
    ::s = s;
    memset(len, 0x3f, sizeof len);
    for(int i = 0; i < n - 1; i++){
        adj[h[i][0]].pb({h[i][1], l[i]});
        adj[h[i][1]].pb({h[i][0], l[i]});
    }

    decomp(1);
    return (ans == N ? -1 : ans);
}

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