제출 #106646

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
106646		doowey	경주 (Race) (IOI11_race)	C++14	100 / 100	819 ms	36156 KiB

race

#include <bits/stdc++.h>
#include "race.h"

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

#define fi first
#define se second
#define mp make_pair

const int N = (int)2e5 + 9;
const int MX = (int)1e6 + 9;
const int inf = (int)1e9 + 1;
int K;
int bes[MX];
vector<pii> T[N];

bool use[MX];
int subt[N];

int res = inf;


void dfs1(int u, int par){
    subt[u] = 1;
    for(auto x : T[u]){
        if(use[x.fi] || x.fi == par) continue;
        dfs1(x.fi, u);
        subt[u] += subt[x.fi];
    }
}

vector<pii> dd;
void dfs2(int u, int par, int sd, int ln){
    if(sd > K)
        return;
    dd.push_back(mp(sd, ln));
    for(auto x : T[u]){
        if(use[x.fi] || x.fi == par) continue;
        dfs2(x.fi, u, sd + x.se, ln + 1);
    }
}

void split(int node){
    dfs1(node, -1);
    int par = -1;
    int atl = subt[node] / 2;
    bool ok = true;
    while(ok){
        ok = false;
        for(auto x : T[node]){
            if(x.fi == par || use[x.fi])continue;
            if(subt[x.fi] > atl){
                par = node;
                node = x.fi;
                ok = true;
                break;
            }
        }
    }

    bes[0] = 0;
    vector<int> er;
    for(auto x : T[node]){
        if(use[x.fi]) continue;
        dd.clear();
        dfs2(x.fi, node, x.se, +1);
        for(auto p : dd){
            res = min(res, p.se + bes[K - p.fi]);
            er.push_back(p.fi);
        }
        for(auto p : dd){
            bes[p.fi] = min(bes[p.fi], p.se);
        }
    }
    for(auto x : er)
        bes[x] = inf;
    use[node] = true;
    for(auto x : T[node]){
        if(!use[x.fi])
            split(x.fi);
    }
    
}

int best_path(int n, int k, int h[][2], int ln[]){
    K = k;
    for(int i = 0 ;i  < MX; i ++ )
        bes[i] = inf;
    for(int i = 0 ; i < n-  1; i ++ ){
        T[h[i][0]].push_back(mp(h[i][1], ln[i]));
        T[h[i][1]].push_back(mp(h[i][0], ln[i]));
    }
    split(0);
    return (res == inf ? -1 : res);
}

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