Submission #563426

#	Time	Username	Problem	Language	Result	Execution time	Memory
563426		hibiki	Race (IOI11_race)	C++11	0 / 100	3 ms	4948 KiB

race

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

#define pb push_back
#define f first
#define s second

// global
int ans = 1e9, n, k;
vector<pair<int,long long> > v[200005];

// centroid
int sz[200005];
bool visited[200005];

// query & update
map<long long,int> mp;

void query(int nw,int fa,int dep,long long total)
{
    if(mp.count(k - total))
        ans = min(ans, dep + mp[k - total]);
    for(auto go: v[nw])
        if(go.f != fa && !visited[go.f])
            query(go.f, nw, dep + 1, total + go.s);
}

void update(int nw,int fa,int dep, long long total)
{
    if(mp.count(total))
        mp[total] = min(mp[total], dep);
    else
        mp[total] = dep;
    for(auto go: v[nw])
        if(go.f != fa && !visited[go.f])
            query(go.f, nw, dep + 1, total + go.s);
}

int re_size(int nw,int fa)
{
    sz[nw] = 1;
    for(auto go: v[nw])
        if(go.f != fa && !visited[go.f])
            sz[nw] += re_size(go.f,nw);
    return sz[nw];
}

int fi_cen(int nw,int fa,int sum)
{
    for(auto go: v[nw])
        if(go.f != fa && !visited[go.f] && sz[go.f] > sum/2)
            return fi_cen(go.f,nw,sum);
    return nw;
}

void centroid_decomp(int nw)
{
    int cen = fi_cen(nw, -1, re_size(nw, -1));
    visited[cen] = true;

    mp.clear();
    mp.emplace(0, 0);
    for(auto go: v[cen])
    {
        if(!visited[go.f])
        {
            query(go.f, cen, 1, go.s);
            update(go.f, cen, 1, go.s);
        }
    }

    for(auto go: v[cen])
        if(!visited[go.f])
            centroid_decomp(go.f);
}

int best_path(int N, int K, int H[][2], int L[])
{
    n = N, k = K;
    for(int i = 0; i < n - 1; i++)
    {
        v[H[i][0]].emplace_back(H[i][1], L[i]);
        v[H[i][1]].emplace_back(H[i][0], L[i]);
    }

    centroid_decomp(0);

    if(ans == 1e9)
        return -1;

    return ans;
}

// int a,b;
// int send[200005][2],send2[200005];
// int main()
// {
//     scanf("%d %d",&a,&b);
//     for(int i = 0; i < a - 1; i++)
//         scanf("%d %d %d",&send[i][0],&send[i][1],&send2[i]);
//     printf("%d",best_path(a, b, send, send2));
//     return 0;
// }

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