Submission #580867

#	Time	Username	Problem	Language	Result	Execution time	Memory
580867		benson1029	Race (IOI11_race)	C++14	31 / 100	880 ms	53544 KiB

race

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

vector< pair<int,int> > edg[200005];
int k;
bool solved[200005];
int compsize[200005];
int mxdeg, centroid;
vector< pair<long long, int> > v;
set< pair<long long, int> > v2;
int ans = 1e9;

void findcentroid(int x, int p, int totsize) {
	int deg = 0;
	compsize[x] = 1;
	if(p!=-1) ++deg;
	for(auto i:edg[x]) {
		if(!solved[i.first] && i.first!=p) {
			findcentroid(i.first, x, totsize);
			compsize[x] += compsize[i.first];
			++deg;
		}
	}
	bool ok = true;
	for(auto i:edg[x]) {
		if(!solved[i.first] && i.first!=p) {
			if(compsize[i.first] > totsize/2) ok = false;
		}
	}
	if(totsize - compsize[x] > totsize/2) ok = false;
	if(ok) centroid = x;
}

void solve(int x);

void findandsolve(int x) {
	mxdeg = -1;
	findcentroid(x, -1, compsize[x]);
	solve(centroid);
}

void dfs(int x, int p, long long len, int cnt) {
	v.push_back({len, cnt});
	for(auto i:edg[x]) {
		if(solved[i.first]) continue;
		if(i.first != p) {
			dfs(i.first, x, len+i.second, cnt+1);
		}
	}
}

void solve(int x) {
	v.clear(); v2.clear();
	v2.insert({0, 0});
	solved[x] = true;
	for(auto i:edg[x]) {
		if(solved[i.first]) continue;
		v.clear();
		dfs(i.first, -1, i.second, 1);
		sort(v.begin(), v.end());
		for(auto i:v) {
			auto tmp = v2.lower_bound(make_pair(k-i.first, 0));
			if(tmp!=v2.end() && (*tmp).first == k-i.first) {
				ans = min(ans, (*tmp).second + i.second);
			}
		}
		for(auto i:v) {
			v2.insert(i);
		}
	}
	for(auto i:edg[x]) {
		if(solved[i.first]) continue;
		findandsolve(i.first);
	}
}

int best_path(int N, int K, int H[][2], int L[])
{
	k = K;
	for(int i=0; i<N-1; i++) {
		edg[H[i][0]].push_back({H[i][1], L[i]});
		edg[H[i][1]].push_back({H[i][0], L[i]});
	}
	compsize[0] = N;
	findandsolve(0);
	if(ans==1e9) return -1;
	return ans;
}

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