Submission #16694

#	Time	Username	Problem	Language	Result	Execution time	Memory
16694		suhgyuho_william	Race (IOI11_race)	C++98	100 / 100	854 ms	35520 KiB

race

#include "race.h"
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;

int n,k;
int answer = 999999999;
vector<pair<int,int> > edge[200002];
queue<pair<int,int> > q,qt;
int root[1000002],small[1000002];
bool check[200002];
queue<int> qv;
int downcnt[200002];
int max_subtree[200002];

int j,nextv,tmp;
pair<int,int> top;

int make_qv(int x){
    int i;

    check[x] = true;
    qv.push(x);
    downcnt[x] = max_subtree[x] = 0;
    for(i=0; i<edge[x].size(); i++){
        nextv = edge[x][i].first;
        if(!check[nextv]){
            tmp = make_qv(nextv);
            downcnt[x] += tmp;
            if(max_subtree[x] < tmp) max_subtree[x] = tmp;
        }
    }
    check[x] = false;
    return (downcnt[x]+1);
}

int find_middle(int x){
    int i,below_x;
    int big = 0,v;

    below_x = make_qv(x);
    while(!qv.empty()){
        v = qv.front();
        tmp = min(below_x - max_subtree[v],max_subtree[v]+1);
        if(big < tmp){
            big = tmp;
            x = v;
        }
        qv.pop();
    }

    return x;
}

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

    if(sum > k) return;
    check[v] = true;
    q.push(make_pair(sum,cnt));
    qt.push(make_pair(sum,cnt));

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

// T(n) = 2T(n/2) + O(n);

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

    check[v] = true;

    root[0] = v;
    small[0] = 0;
    for(i=0; i<edge[v].size(); i++){
        nextv = edge[v][i].first;
        if(check[nextv]) continue;
        dfs(nextv,edge[v][i].second,1);

        while(!q.empty()){
            top = q.front();
            if(root[k-top.first] == v) answer = min(answer,small[k-top.first] + top.second);
            q.pop();
        }
        while(!qt.empty()){
            top = qt.front();
            qt.pop();

            if(root[top.first] != v){
                root[top.first] = v;
                small[top.first] = top.second;
            }else if(small[top.first] > top.second) small[top.first] = top.second;
        }
    }

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

int best_path(int N, int K, int H[][2], int L[])
{
    n = N; k = K;
    for(j=0; j<n-1; j++){
        edge[H[j][0]].push_back(make_pair(H[j][1],L[j]));
        edge[H[j][1]].push_back(make_pair(H[j][0],L[j]));
    }
    for(j=0; j<=k; j++) root[j] = -1;

    race(0);

    if(answer == 999999999) answer = -1;
    return answer;
}

Compilation message (stderr)

race.cpp: In function 'int make_qv(int)':
race.cpp:26:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0; i<edge[x].size(); i++){
              ~^~~~~~~~~~~~~~~
race.cpp: In function 'int find_middle(int)':
race.cpp:39:9: warning: unused variable 'i' [-Wunused-variable]
     int i,below_x;
         ^
race.cpp: In function 'void dfs(int, int, int)':
race.cpp:64:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0; i<edge[v].size(); i++){
              ~^~~~~~~~~~~~~~~
race.cpp: In function 'void race(int)':
race.cpp:82:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0; i<edge[v].size(); i++){
              ~^~~~~~~~~~~~~~~
race.cpp:103:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(i=0; i<edge[v].size(); i++){
              ~^~~~~~~~~~~~~~~

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