Submission #715151

#	Time	Username	Problem	Language	Result	Execution time	Memory
715151		vjudge1	Towns (IOI15_towns)	C++17	100 / 100	16 ms	884 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>
using namespace std;
 
int hubDistance(int n, int sub) {
	vector<int> d0(n), d1(n);
	int mx = 0, R = 1e9;
	for (int i = 1; i < n; ++i) {
		d0[i] = getDistance(0, i);
		if (d0[i] > d0[mx]) mx = i;
	}
	d1[0] = d0[mx];
	int d = d0[mx];
	map<int, vector<int>> groups;
	for (int i = 1; i < n; ++i) if (i != mx) {
		d1[i] = getDistance(mx, i);
		groups[(d1[i] - d0[i] + d0[mx]) / 2].push_back(i);
		d = max(d, d1[i]);
	}
	int hub = 0, lft = 1, rht = n-1;
	for (auto g: groups) {
		R = min(R, max(g.first, d-g.first));
	}
	// cerr << mx << endl;
	for (auto g: groups) {
		rht -= g.second.size();
		if (max(g.first, d-g.first) == R) {
			if (lft <= n/2 && rht <= n/2) {
				int mst = -1, cnt=0, qcnt=0;
				vector<int> head(n), sz(n);
				auto same_st = [&](int a, int b) {qcnt++;return a == b || getDistance(a, b) != d1[a]+d1[b] - 2*g.first;};
				for (int i = 0; i < g.second.size(); ++i) {
					if (!cnt) mst = g.second[i];
					if (same_st(mst, g.second[i])) {
						cnt++;
						head[g.second[i]] = mst;
						sz[mst]++;
					} else {
						cnt--;
						head[g.second[i]] = g.second[i];
						sz[g.second[i]] = 1;
					}
				}
				bool ignore = 0;
				for (int i = g.second.size(); i--;) if (g.second[i] != mst) {
					if (head[g.second[i]] == g.second[i]) {
						if (same_st(mst, g.second[i])) {
							sz[mst]+=sz[g.second[i]];
						}
					}
				}
				if (sz[mst] > n/2) return -R;
				return R;
			}
		}
		lft += g.second.size();
	}
	return -R;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:26:24: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   26 |   rht -= g.second.size();
      |                        ^
towns.cpp:32:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |     for (int i = 0; i < g.second.size(); ++i) {
      |                     ~~^~~~~~~~~~~~~~~~~
towns.cpp:45:31: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   45 |     for (int i = g.second.size(); i--;) if (g.second[i] != mst) {
      |                  ~~~~~~~~~~~~~^~
towns.cpp:44:10: warning: unused variable 'ignore' [-Wunused-variable]
   44 |     bool ignore = 0;
      |          ^~~~~~
towns.cpp:56:24: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   56 |   lft += g.second.size();
      |                        ^
towns.cpp:20:6: warning: unused variable 'hub' [-Wunused-variable]
   20 |  int hub = 0, lft = 1, rht = n-1;
      |      ^~~
towns.cpp:5:28: warning: unused parameter 'sub' [-Wunused-parameter]
    5 | int hubDistance(int n, int sub) {
      |                        ~~~~^~~

• Subtask 1: 13 / 13
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 10 / 10
• Subtask 5: 13 / 13
• Subtask 6: 39 / 39