Submission #464826

#	Time	Username	Problem	Language	Result	Execution time	Memory
464826		jk410	Race (IOI11_race)	C++17	100 / 100	548 ms	35132 KiB

race

#include <bits/stdc++.h>
#include "race.h"
using namespace std;
struct edge{
    int v,cost;
};
const int INF=1e9;
int N,K,Ans,t;
int Size[200000],Min_Depth[1000001],Min_Depth_Visited[1000001];
bool Visited[200000];
vector<edge> Edge[200000];
int get_size(int v,int par=-1){
    int &ret=Size[v]=1;
    for (edge i:Edge[v]){
        if (Visited[i.v]||i.v==par)
            continue;
        ret+=get_size(i.v,v);
    }
    return ret;
}
int get_cent(int v,int sz,int par=-1){
    for (edge i:Edge[v]){
        if (Visited[i.v]||i.v==par)
            continue;
        if (Size[i.v]*2>sz)
            return get_cent(i.v,sz,v);
    }
    return v;
}
int dfs1(int v,int dist,int par,int depth=1){
    if (dist>K)
        return INF;
    int ret=INF;
    if (Min_Depth_Visited[K-dist]==t)
        ret=depth+Min_Depth[K-dist];
    for (edge i:Edge[v]){
        if (Visited[i.v]||i.v==par)
            continue;
        ret=min(ret,dfs1(i.v,dist+i.cost,v,depth+1));
    }
    return ret;
}
void dfs2(int v,int dist,int par,int depth=1){
    if (dist>K)
        return;
    if (Min_Depth_Visited[dist]!=t){
        Min_Depth_Visited[dist]=t;
        Min_Depth[dist]=depth;
    }
    else
        Min_Depth[dist]=min(Min_Depth[dist],depth);
    for (edge i:Edge[v]){
        if (Visited[i.v]||i.v==par)
            continue;
        dfs2(i.v,dist+i.cost,v,depth+1);
    }
}
int solve(int v){
    t++;
    Min_Depth_Visited[0]=t;
    int ret=INF;
    int cent=get_cent(v,get_size(v));
    Visited[cent]=true;
    for (edge i:Edge[cent]){
        if (Visited[i.v])
            continue;
        ret=min(ret,dfs1(i.v,i.cost,cent));
        dfs2(i.v,i.cost,cent);
    }
    for (edge i:Edge[cent]){
        if (Visited[i.v])
            continue;
        ret=min(ret,solve(i.v));
    }
    return ret;
}
int best_path(int n,int k,int h[][2],int l[]){
    N=n;
    K=k;
    for (int i=0; i<N-1; i++){
        Edge[h[i][0]].push_back({h[i][1],l[i]});
        Edge[h[i][1]].push_back({h[i][0],l[i]});
    }
    Ans=solve(0);
    if (Ans==INF)
        Ans=-1;
    return Ans;
}

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