Submission #16671

#	Time	Username	Problem	Language	Result	Execution time	Memory
16671		suhgyuho_william	Race (IOI11_race)	C++98	0 / 100	5 ms	4984 KiB

race

#include "race.h"
#include <vector>
using namespace std;
// frozen

int i,n,k;
int answer = -1;
vector<pair<int,int> > edge[200002];
bool check[200002];
int half_sum[1000002];

int find_middle(int x){
    return x;
}

void dfs(int v,int sum,int cnt){
    int i,sizes;
    int nextv,cost;

    check[v] = true;
    if(half_sum[sum] == -1) half_sum[sum] = cnt;
    else if(half_sum[sum] > cnt) half_sum[sum] = cnt;
    sizes = edge[v].size();
    for(i=0; i<sizes; i++){
        nextv = edge[v][i].first;
        cost = edge[v][i].second;
        if(check[nextv]) continue;
        dfs(nextv,sum+cost,cnt+1);
    }
    check[v] = false;
}

void get(int v){
    int i;

    for(i=0; i<=k; i++) half_sum[i] = -1;
    dfs(v,0,0);
}

void race(int x){
    int i,sizes;
    int nextv;
    int v = find_middle(x);

    get(v);
    check[v] = true;

    for(i=0; i<k/2; i++){
        if(half_sum[i] != -1 && half_sum[k-i] != -1){
            if(answer == -1) answer = half_sum[i]+half_sum[k-i];
            else if(answer > half_sum[i]+half_sum[k-i]) answer = half_sum[i]+half_sum[k-i];
        }
    }

    sizes = edge[v].size();
    for(i=0; i<sizes; i++){
        nextv = edge[v][i].first;
        if(!check[nextv]) race(nextv);
    }
}

int best_path(int N, int K, int H[][2], int L[])
{
    int i;

    n = N; k = K;
    for(i=0; i<n-1; i++){
        edge[H[i][0]].push_back(make_pair(H[i][1],L[i]));
        edge[H[i][1]].push_back(make_pair(H[i][0],L[i]));
    }

    race(0);

    return answer;
}

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