Submission #200636

#	Time	Username	Problem	Language	Result	Execution time	Memory
200636		wilwxk	City Mapping (NOI18_citymapping)	C++14	70.13 / 100	14 ms	6904 KiB

citymapping

#include "citymapping.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
 
const int MAXN = 1e3+5;
ll dist[MAXN][MAXN];
vector<tuple<int, int, int> > ans;
vector<int> subtree[MAXN];
ll further[MAXN][2];
mt19937 rng(time(0));
int n;
 
ll query(int a, int b) {
	if(a == b) return 0;
	if(a > b) swap(a, b);
	if(dist[a][b]) return dist[a][b];
	// printf("query %d %d\n", a, b);
	return dist[a][b] = get_distance(a, b);
}
 
void solve(int cur) {
	if(subtree[cur].size() == 1) return;
	int x = further[cur][0];
	int y = rng()%subtree[cur].size();
	while(subtree[cur][y] == x) y = rng()%subtree[cur].size();
	y = subtree[cur][y];
	// printf("solve %d >> %d %d\n", cur, x, y); for(auto vertex : subtree[cur]) printf("%d ", vertex); cout << endl;
 
	vector<pair<ll, int> > line;
	vector<pair<ll, int> > aux;
	for(int vertex : subtree[cur]) {
		ll val = query(x, vertex) + query(y, vertex) - query(x, y); val /= 2;
		if(val == 0) line.push_back({query(x, vertex), vertex});
		val = query(x, y) - query(vertex, y) + val;
		aux.push_back({val, vertex});
	}
	sort(line.begin(), line.end());
	sort(aux.begin(), aux.end());
	subtree[cur].clear();
	further[cur][0] = 0;
	further[cur][1] = -1;
 
	int p = 0;
	for(int i = 0; i < line.size(); i++) {
		int vertex = line[i].second;
		ll dx = line[i].first;
		while(p < aux.size() && aux[p].first == dx) {
			ll val = query(x, aux[p].second) - dx;
			if(val > further[vertex][1]) further[vertex][0] = aux[p].second, further[vertex][1] = val;
			subtree[vertex].push_back(aux[p++].second);
		}
		if(i != 0) ans.push_back({vertex, line[i-1].second, line[i].first-line[i-1].first});
	}
 
	for(auto item : line) solve(item.second);
}
 
void find_roads(int N, int Q, int A[], int B[], int W[]) {
	n = N;
 
	for(int i = 1; i <= n; i++) subtree[n+1].push_back(i);
	further[n+1][0] = rng()%(n+1)+1;
	solve(n+1);
 
	for(int i = 0; i < ans.size(); i++) tie(A[i], B[i], W[i]) = ans[i];
}

Compilation message (stderr)

citymapping.cpp: In function 'void solve(int)':
citymapping.cpp:45:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < line.size(); i++) {
                 ~~^~~~~~~~~~~~~
citymapping.cpp:48:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while(p < aux.size() && aux[p].first == dx) {
         ~~^~~~~~~~~~~~
citymapping.cpp: In function 'void find_roads(int, int, int*, int*, int*)':
citymapping.cpp:66:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < ans.size(); i++) tie(A[i], B[i], W[i]) = ans[i];
                 ~~^~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 16 / 16
• Subtask 3: 13 / 13
• Subtask 4: 19 / 19
• Subtask 5: 13.13 / 43