Submission #432902

#	Time	Username	Problem	Language	Result	Execution time	Memory
432902		Kevin_Zhang_TW	Towns (IOI15_towns)	C++17	61 / 100	21 ms	1100 KiB

towns

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb emplace_back
#define AI(i) begin(i), end(i)
template<class T> bool chmin(T &a, T b) { return b < a && (a = b, true); }
template<class T> bool chmax(T &a, T b) { return a < b && (a = b, true); }
#ifdef KEV
#define DE(args...) kout("[ " + string(#args) + " ] = ", args)
void kout() { cerr << endl; }
template<class T, class ...U> void kout(T a, U ...b) { cerr << a << ' ', kout(b...); }
template<class T> void debug(T l, T r) { while (l != r) cerr << *l << " \n"[next(l)==r], ++l; }
#else
#define DE(...) 0
#define debug(...) 0
#endif

const int MAX_N = 200;
#include "towns.h"

int mem_dis[MAX_N][MAX_N], n, h[MAX_N];
int dis(int a, int b) {
	if (mem_dis[a][b] || a == b) return mem_dis[a][b];
	return mem_dis[a][b] = mem_dis[b][a] = getDistance(a, b);
}

int get_far(int x) {
	int d = 0, g = -1;
	for (int i = 0;i < n;++i) if (i != x)
		if (chmax(d, dis(x, i)))
			g = i;
	return g;
}

bool too_big(int x) { return x > n / 2; }

int hubDistance(int N, int sub) {
	memset(mem_dis, 0, sizeof(mem_dis));
	n = N;

	int f = get_far(0), g = get_far(f);

	map<int, vector<int>> cnt;
	for (int i = 0;i < n;++i) {
		int y = dis(f, i), z = dis(g, i), x = dis(f, g);
		h[i] = (y + z - x) / 2;
		//++cnt[y - h[i]];
		cnt[y - h[i]].pb(i);
	}

	int ret = dis(f, g);

	for (auto [a, _] : cnt)
		chmin(ret, max(a, dis(f, g) - a));

	auto valid = [&](vector<int> child) {
		if (!too_big(child.size())) return true; 
		if (sub == 2 || sub == 4) return !too_big(child.size());

		int x = -1, cnt = 0;
		for (int y : child) {
			if (cnt == 0) {
				x = y;
				++cnt;
				continue;
			}
			if (h[x] + h[y] != dis(x, y)) ++cnt;
			else --cnt;
			if (too_big(cnt)) return false;
		} 

		int req = n / 2 + 1;
		{
			int a = req, b = child.size() - req;
			if (cnt < a - b)
				return true;
		}
		cnt = 0;
		for (int y : child) {
			if (h[x] + h[y] != dis(x, y))
				++cnt;
			if (too_big(cnt)) return false;
		}
		return !too_big(cnt); 
	};

	bool has_hub = false;

	for (auto [a, child] : cnt)
		if (max(a, dis(f, g) - a) == ret) {
			int l = 0, r = 0;
			for (auto [w, c] : cnt) {
				if (w < a) l += c.size();
				if (w > a) r += c.size();
			}
			if (too_big(max(l, r))) continue;

			if (valid(child)) {
				has_hub = true;
				break;
			}
		}

	if (!has_hub) ret *= -1;
	return ret;
}

Compilation message (stderr)

towns.cpp: In lambda function:
towns.cpp:57:26: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   57 |   if (!too_big(child.size())) return true;
      |                ~~~~~~~~~~^~
towns.cpp:58:55: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   58 |   if (sub == 2 || sub == 4) return !too_big(child.size());
      |                                             ~~~~~~~~~~^~
towns.cpp:60:15: warning: declaration of 'cnt' shadows a previous local [-Wshadow]
   60 |   int x = -1, cnt = 0;
      |               ^~~
towns.cpp:43:24: note: shadowed declaration is here
   43 |  map<int, vector<int>> cnt;
      |                        ^~~
towns.cpp:74:34: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   74 |    int a = req, b = child.size() - req;
      |                     ~~~~~~~~~~~~~^~~~~
towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:93:28: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   93 |     if (w < a) l += c.size();
      |                            ^
towns.cpp:94:28: warning: conversion from 'std::vector<int>::size_type' {aka 'long unsigned int'} to 'int' may change value [-Wconversion]
   94 |     if (w > a) r += c.size();
      |                            ^

• Subtask 1: 13 / 13
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 10 / 10
• Subtask 5: 13 / 13
• Subtask 6: 0 / 39