Submission #306518

#	Time	Username	Problem	Language	Result	Execution time	Memory
306518		tengiz05	Dreaming (IOI13_dreaming)	C++14	100 / 100	182 ms	29432 KiB

dreaming

#include "dreaming.h"
#include <bits/stdc++.h>
using namespace std;
int n;
const int N = 1e5+5;
bool used[N];
long long depth[N];
long long dp[N];
vector<pair<int, long long>> edges[N];
vector<long long> a[N];
// dfs for calculating dp. (dp[i] - maximum depth)
void dfs(int u, int p){
	used[u] = true;
	dp[u] = 0;
	a[u].push_back(0);a[u].push_back(0);
	for(auto X : edges[u]){
		int v = X.first;
		long long cost = X.second;
		if(v == p)continue;
		dfs(v, u);
		dp[u] = max(dp[u], dp[v]+cost);
		a[u].push_back(dp[v]+cost);
	}
	sort(a[u].begin(), a[u].end());
	reverse(a[u].begin(), a[u].end());
}
 
//dfs for rerooting
long long mn;
void dfs2(int u, int p, long long T){
	long long dpu = dp[u];
	for(auto X : edges[u]){
		int v = X.first;
		long long cost = X.second;
		if(v == p)continue;
		long long tmp = dp[v];
		if(dp[v]+cost == a[u][0])dp[u] = a[u][1];
		if(u != p)dp[u] = max(dp[u], dp[p] + T);
		dp[v] = max(dp[v], dp[u] + cost);
		mn = min(mn, dp[v]);
		dfs2(v, u, cost);
		dp[v] = tmp;
		dp[u] = dpu;
	}
}
 
//calculate best center for the tree
long long calculate_center(int u){
	dfs(u, u);
	mn = dp[u];
	dfs2(u, u ,0);
	return mn;
}
int travelTime(int _N, int M, int L, int A[], int B[], int T[]) {
	n = _N;
	for(int i=0;i<M;i++){
		edges[A[i]].push_back({B[i], T[i]});
		edges[B[i]].push_back({A[i], T[i]});
	}
	vector<long long> v;
	for(int i=0;i<n;i++){
		if(!used[i]){
			v.push_back(calculate_center(i));
		}
	}
	sort(v.begin(), v.end());
	reverse(v.begin(), v.end());

	if(v.size() == 1){
		long long m = 0;
		for(int i=0;i<n;i++){
			m = max(m, a[i][0]+a[i][1]);
		}
		return m;
	}
	else {
		long long m = 0;
		for(int i=0;i<n;i++){
			m = max(m, a[i][0]+a[i][1]);
		}
		return max(v[0]+v[1]+L, max(m, ((v.size()>=3)? v[1]+v[2]+2*L : 0ll)));
	}
}

• Subtask 1: 14 / 14
• Subtask 2: 10 / 10
• Subtask 3: 23 / 23
• Subtask 4: 18 / 18
• Subtask 5: 12 / 12
• Subtask 6: 23 / 23