Submission #702427

#	Time	Username	Problem	Language	Result	Execution time	Memory
702427		GusterGoose27	City Mapping (NOI18_citymapping)	C++11	0 / 100	2 ms	596 KiB

citymapping

#include "citymapping.h"

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, int> pli;

const int MAXN = 1000;
int t = 0;
mt19937 rng(0);
ll dist[2][MAXN];

void make_ans(vector<int> &vals, int a[], int b[], int w[]) {
	if (vals.size() == 1) return;
	if (vals.size() == 2) {
		a[t] = vals[0];
		b[t] = vals[1];
		w[t] = get_distance(vals[0], vals[1]);
		t++;
		return;
	}
	int n = vals.size();
	int f = rng()%n;
	int mx = -1;
	for (int i = 0; i < n; i++) {
		if (i == f) continue;
		dist[0][i] = get_distance(vals[i], vals[f]);
		if (mx == -1 || dist[0][i] > dist[0][mx]) mx = i;
	}
	dist[0][f] = 0;
	for (int i = 0; i < n; i++) {
		if (i == f || i == mx) continue;
		dist[1][i] = get_distance(vals[i], vals[mx]);
	}
	dist[1][mx] = 0;
	dist[1][f] = dist[0][mx];
	vector<pli> path;
	map<ll, vector<int>> buckets;
	for (int i = 0; i < n; i++) {
		if (dist[0][i]+dist[1][i] == dist[0][mx]) {
			path.push_back(pli(dist[0][i], i));
		}
	}
	sort(path.begin(), path.end());
	for (int i = 0; i < path.size()-1; i++) {
		a[t] = vals[path[i].second];
		b[t] = vals[path[i+1].second];
		w[t] = dist[0][i+1]-dist[0][i];
		t++;
	}
	for (int i = 0; i < n; i++) {
		buckets[dist[1][i]-dist[0][i]].push_back(vals[i]);
	}
	for (auto it: buckets) {
		make_ans(it.second, a, b, w);
	}
}

void find_roads(int n, int q, int a[], int b[], int w[]) {
	vector<int> v(n);
	iota(v.begin(), v.end(), 1);
	make_ans(v, a, b, w);
	assert(t == n-1);
	return;
}

Compilation message (stderr)

citymapping.cpp: In function 'void make_ans(std::vector<int>&, int*, int*, int*)':
citymapping.cpp:48:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |  for (int i = 0; i < path.size()-1; i++) {
      |                  ~~^~~~~~~~~~~~~~~

• Subtask 1: 0 / 9
• Subtask 2: 0 / 16
• Subtask 3: 0 / 13
• Subtask 4: 0 / 19
• Subtask 5: 0 / 43