Submission #471066

#	Time	Username	Problem	Language	Result	Execution time	Memory
471066		jli12345	Race (IOI11_race)	C++14	0 / 100	3 ms	4940 KiB

race

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

void fastIO(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
}

typedef long long ll;

vector<pair<int, int> > edges[200100];
int sub[200100];
bool rem[200100];

int LEN;


void dfs(int node, int pa = 0){
    sub[node] = 1;
    for (pair<int, int> nx : edges[node]){
        if (nx.first == pa || rem[nx.first])
            continue;
        dfs(nx.first, node);    
        sub[node] += sub[nx.first];
    }
}

int centroid(int node, int sz, int pa = 0){
    for (pair<int, int> nx : edges[node]){
        if (nx.first == pa || rem[nx.first])
            continue;
        if (sub[nx.first] > sz/2)
            return centroid(nx.first, sz, node);    
    }
    return node;
}

void dfs2(int node, ll dep, int cur, map<ll, int> &mp, int pa = 0){
    if (mp.count(dep))
        mp[dep] = min(mp[dep], cur);
    else
        mp[dep] = cur;
    for (pair<int, int> nx : edges[node]){
        if (nx.first == pa || rem[nx.first])
            continue;
        dfs2(nx.first, dep+nx.second, cur+1, mp, node);
    }
}

int INF = 0x3f3f3f3f;

int decomp(int node){
    dfs(node);
    int cent = centroid(node, sub[node]);
    rem[cent] = true;
    map<ll, int> mp;
    int curmin = INF;
    mp[0] = 0;
    for (pair<int, int> nx : edges[cent]){
        if (rem[nx.first])
            continue;
        map<ll, int> tmp;
        dfs2(nx.first, nx.second, 1, tmp);
        for (auto it = tmp.begin(); it != tmp.end(); it++){
            if (mp.count(LEN-(*it).first))
                curmin = min(curmin, (*it).second+mp[LEN-(*it).first]);
        }
        for (auto it = tmp.begin(); it != tmp.end(); it++){
            if (!mp.count((*it).first))
                mp[(*it).first] = (*it).second;
            else
                mp[(*it).first] = min(mp[(*it).first], (*it).second);
        }
    }
    int totmin = curmin;
    for (pair<int, int> nx : edges[cent]){
        if (rem[nx.first])
            continue;
        totmin = min(totmin, decomp(nx.first));
    }
    if (totmin == INF)
        return -1;
    return totmin;
}

int best_path(int N, int K, int H[][2], int *L){
    LEN = K;
    for (int i = 0; i < N-1; i++){
        int a = H[i][0], b = H[i][1];
        a++, b++;
        edges[a].push_back({b, L[i]});
        edges[b].push_back({a, L[i]});
    }
    return decomp(1);
}

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