Submission #106625

#	Time	Username	Problem	Language	Result	Execution time	Memory
106625		doowey	Race (IOI11_race)	C++14	0 / 100	12 ms	5120 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;

vector<pii> T[N];
bool use[N];
int subt[N];
int dist[N];

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

int K;

int res = -1;

vector<pii> tti;

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

const int KK = (int)1e6 + 9;
int has[KK];

int cnt = 0;

void split(int node){
    ++ cnt;
    dfs1(node, -1);
    int atl = subt[node] / 2;
    int par = -1;
    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;
            }
        }
    }
    has[0] = 0;
    vector<int> al;
    for(auto x : T[node]){
        if(!use[x.fi]){
            tti.clear();
            dfs2(x.fi, node, node, x.se, 1);
            for(auto p : tti){
                if(has[K-p.fi] != -1){
                    if(res == -1 || res > p.se + has[K - p.fi])
                        res = p.se + has[K - p.fi];
                }
            }
            for(auto p : tti){
                if(has[p.fi] == -1 || has[p.fi] < p.se)
                    has[p.fi] = p.se;
                al.push_back(p.fi);
            }
        }
    }
    for(auto p : al) has[p] = -1;
    use[node] = true;
    for(auto x : T[node]){
        if(use[x.fi])
            continue;
        split(x.fi);
    }
    
}

int best_path(int n, int k, int h[][2], int ln[]){
    K = k;
    for(int i = 0 ; i <= K; i ++ )
        has[i] = -1;
    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;
    
}

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