Submission #492542

#	Time	Username	Problem	Language	Result	Execution time	Memory
492542		1ne	Race (IOI11_race)	C++14	0 / 100	11 ms	15568 KiB

race

/*
 *    author:    Apiram
 *    created:   08.12.2021 01:06:00
*/

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

vector<vector<pair<int,int>>>adj(1e5);
vector<vector<int>>sparce(1e5,vector<int>(20,-1));
vector<int>depth(1e5,0);
vector<int64_t>dist(1e5,0);

void getsparce(int u,int par){
	for (auto x:adj[u]){
		if (x.first!=par){
			sparce[x.first][0] = u;
			depth[x.first]=depth[u]+1;
			dist[x.first] = dist[u] + x.second;
			getsparce(x.first,u);
		}
	}
}
int lca(int u,int v){
	if (depth[u]<depth[v]){
		swap(u,v);
	}
	for (int i = 19;i>=0;--i){
		if (sparce[u][i]!=-1)
		if (depth[sparce[u][i]]>=depth[v]){
			u=sparce[u][i];
		}
	}
	if (u==v)return u;
	for (int i = 19;i>=0;--i){
		if (sparce[u][i]!=sparce[v][i]){
			u=sparce[u][i];
			v=sparce[v][i];
		}
	}
	return sparce[u][0];
}
pair<int,int64_t> distt(int u,int v){
	int l = lca(u,v);
	return {depth[u] + depth[v] - 2*depth[l],dist[u] + dist[v] - 2*dist[l]};
}
void preprocess(int n){
	getsparce(0,-1);
	for (int i = 1;i<20;++i){
		for (int j = 0;j<n;++j){
			if (sparce[j][i-1]!=-1){
				sparce[j][i] = sparce[sparce[j][i-1]][i-1];
			}
		}
	}
}
int anss = INT_MAX;
void dfs(int left,int right,int k,int par1,int par2){
	auto u = distt(left,right);
	if (u.second<k){
		for (auto x:adj[right]){
			if (x.first!=par2){
			dfs(left,x.first,k,par1,right);
			}
		}
	}
	else if (u.second>k){
		for (auto x:adj[left]){
			if (x.first!=par1){
			dfs(x.first,x.first,k,left,par2);
			}
		}
	}
	else{
		anss = min(u.first,anss);
	}
}
int best_path(int n, int k, int H[][2], int L[])
{
	for (int i = 0;i<n-1;++i){
	   adj[H[i][0]].push_back({H[i][1],L[i]});
	   adj[H[i][1]].push_back({H[i][0],L[i]});	
	}
	preprocess(n);
	dfs(0,0,k,-1,-1);
	if (anss==INT_MAX){
		anss = -1;
	}
	return anss;
}

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