Submission #858271

#	Time	Username	Problem	Language	Result	Execution time	Memory
858271		YassirSalama	Race (IOI11_race)	C++17	0 / 100	3 ms	14684 KiB

race

#include "race.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <iomanip>
#include <cmath>
#include <limits>
#include <map>
#include <utility>
#include <cctype>
#include <string>
#include <cstring>
#include <stack>
#include <queue>
#include <functional>
#include <iterator>
using namespace std;
#define OVL(x,s) for(auto y:x) cout<<y<<s; cout<<"\n";
void dbg_out() { cout << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cout << ' ' << H; dbg_out(T...); }
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__);
#define endl "\n"
#define pb push_back
#define F first
#define S second
#define ll long long
#define mod 1000000007
#define all(v) v.begin(),v.end()
const int MAXN=2e5+100;
const int LOGN=17;
int up[MAXN][LOGN+1];
int par[MAXN];
int n,k;
set<pair<int,int>> v[MAXN];
int depth[MAXN];//the length of the unweightedf path from root to x
int depth2[MAXN];//the length of the weighred path from root to x
void dfslca(int node,int par,int dep){
    depth[node]=depth[par]+1;
    depth2[node]=dep;
    up[node][0]=par;
    for(int i=1;i<=LOGN;i++){
        up[node][i]=up[up[node][i-1]][i-1];
    }
    for(auto x:v[node]){
        if(x.F==par) continue;
        dfslca(x.F,node,dep+x.S);
    }
}
int LCA(int a,int b){
    if(depth[a]<depth[b]) swap(a,b);
    int d=depth[a]-depth[b];
    for(int i=LOGN;i>=0;i--){
        if((1<<i)&d) a=up[a][i];
    }
    if(a==b) return a;
    for(int i=LOGN;i>=0;i--){
        if(up[a][i]==up[b][i]) continue;
        a=up[a][i];
        b=up[b][i];
    }
    return up[a][0];
}
int sub[MAXN];
bool visited[MAXN];
int dfs(int node,int par){
    if(visited[node]) return 0;
    sub[node]=1;
    for(auto x:v[node]){
        if(x.F==par) continue;
        sub[node]+=dfs(x.F,node);
   }
   return sub[node];
}
int dfs2(int node,int par,int n){
    for(auto x:v[node]){
        if(x.F==par) continue;
        if(!visited[x.F]&&sub[x.F]>n/2)
            return dfs2(x.F,node,n);

    }
    return node;
}
void decompose(int node,int parr){
    dfs(node,-1);
    int c=dfs2(node,-1,sub[node]);
    visited[c]=true;
    par[c]=parr;
    for(auto x:v[c]){
        if(!visited[x.F]) decompose(x.F,c);
    }
}
map<int,map<int,pair<int,int>>> mp;
const int INF=1e9;
int dist2(int a,int b){
    return depth2[a]+depth2[b]-2*depth2[LCA(a,b)];
}
int dist1(int a,int b){
    return depth[a]+depth[b]-2*depth[LCA(a,b)];
}
void update(int u){
    int node=u;
    while(node!=-1){
        int a=dist2(node,u);
        int b=dist1(node,u);
        if(mp[node].count(a)&&
            mp[node][a].F==b){
            mp[node][a].S++;
        }else{
            if(mp[node].count(a)) 
                mp[node][a].F=min(mp[node][a].F,b);
            mp[node][a].S=1;
        }
        node=par[node];
    }
}
int ANS=INF;
void query(int u){
    int node=u;
    while(node!=-1){
        int a=dist2(node,u);
        int b=dist1(node,u);
        int target=k-a;
        // dbg(node,u,target,k,a);
        if(mp[node].count(target)){
            if(a==target&&mp[node][a].S>=2) {
                ANS=min(ANS,b+mp[node][a].S);
            }
            else if(a!=target){
                ANS=min(ANS,b+mp[node][target].S);
            }
        }
        node=par[node];
    }
}
int best_path(int N, int K, int H[][2], int L[])
{ 
    for(int i=0;i<N-1;i++) {
        v[H[i][0]].insert({H[i][1],L[i]});
        v[H[i][1]].insert({H[i][0],L[i]});
    }
    k=K;
    dfslca(1,1,0);
    decompose(0,-1);
    // for(int i=0;i<N;i++) dbg(i,par[i]);
    for(int i=0;i<N;i++) update(i);
    for(int i=0;i<N;i++) query(i);
    if(ANS==1e9) return -1;
    return ANS;
}



#ifdef IOI

#define MAX_N 500000

static int N, K;
static int H[MAX_N][2];
static int L[MAX_N];
static int solution;

inline 
void my_assert(int e) {if (!e) abort();}

void read_input()
{
    int i;
    my_assert(2==scanf("%d %d",&N,&K));
    for(i=0; i<N-1; i++)
        my_assert(3==scanf("%d %d %d",&H[i][0],&H[i][1],&L[i]));
    my_assert(1==scanf("%d",&solution));
}

int main()
{
    int ans;
    read_input();
    ans = best_path(N,K,H,L);
    if(ans==solution)
        printf("Correct.\n");
    else
        printf("Incorrect. Returned %d, Expected %d.\n",ans,solution);

    return 0;
}

#endif

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