Submission #60690

#	Time	Username	Problem	Language	Result	Execution time	Memory
60690		reality	Towns (IOI15_towns)	C++17	100 / 100	44 ms	1388 KiB

towns

#include "towns.h"
#include "bits/stdc++.h"
using namespace std;
#define fi first
#define se second
#define ll long long
#define dbg(v) cerr<<#v<<" = "<<v<<'\n'
#define vi vector<int>
#define vl vector <ll>
#define pii pair<int,int>
#define mp make_pair
#define db long double
#define pb push_back
#define all(s) s.begin(),s.end()
template < class T > T smin(T &a,T b) {if (a > b) a = b;return a;}
template < class T > T smax(T &a,T b) {if (a < b) a = b;return a;}
 
const int N = 256;
 
int D[N][N];
 
int get(int x,int y) {
	if (D[x][y] != -1)
		return D[x][y];
	return D[x][y] = D[y][x] = getDistance(x,y);
}
 
int dist[666];

int ans = 2e9;

int x = 0;

int n;

int go(int dt) {
	vi was(n,1);
	int a = 0,b = 0;
	for (int i = 0;i < n;++i) {
		int curr = get(x,i) - dist[i];
		if (curr < dt)
			++a,was[i] = 0;
		if (curr > dt)
			++b,was[i] = 0;
	}
	if (max({a,b}) > (n / 2))
		return -ans;
	auto ok = [&](int A,int B) {
		return get(A,B) != dist[A] + dist[B];
	};
	int cnt = 0;
	int cur = -1;
	vector < pii > ss;
	for (int i = 0;cnt <= (n / 2) && i < n;++i)
		if (was[i]) {
			if (!cnt) {
				cur = i;
				cnt = 1;
				ss.pb(mp(cur,1));
			} else 
			if (ok(cur,i)) {
				++cnt;
				++ss.back().se;
			} else {
				--cnt;
				++ss.back().se;
			}
		}
	if (ss.empty())
		return ans;
	cnt = (cnt + ss.back().se) / 2;
	int sz = ss.size();
	for (int i = 0;i + 1 < sz;++i) {
		if (ok(cur,ss[i].fi))
			cnt += ss[i].se / 2;
		else {
			for (int j = ss[i].fi;j < ss[i].fi + ss[i].se;++j)
				if (!ok(ss[i].fi,j)) {
					cnt += ok(cur,j);
				}
		}
	}
	if (cnt <= (n / 2))
		return ans;
	else
		return -ans;
}

int hubDistance(int N, int sub) {
	n = N;
	srand(time(0));
	const int root = 0;
	memset(D,-1,sizeof(D));
	for (int i = 0;i < n;++i)
		D[i][i] = 0;
	x = root;
	ans = 2e9;
	for (int i = 0;i < n;++i)
		if (get(root,i) > get(root,x))
			x = i;
	int y = x;
	for (int i = 0;i < n;++i)
		if (get(x,i) > get(x,y))
			y = i;
	const int Diam = get(x,y);
	int t = -1;
	for (int i = 0;i < n;++i) {
		dist[i] = (get(root,i) + get(x,i) - get(root,x)) / 2;
		int dx = get(x,i) - dist[i];
		smin(ans,max(Diam - dx,dx));
		if (max(Diam - dx,dx) == ans)
			t = dx;
	}
	return max(go(t),go(Diam - t));
}

Compilation message (stderr)

towns.cpp: In function 'int go(int)':
towns.cpp:72:18: warning: conversion to 'int' from 'std::vector<std::pair<int, int> >::size_type {aka long unsigned int}' may alter its value [-Wconversion]
  int sz = ss.size();
           ~~~~~~~^~
towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:89:31: warning: declaration of 'N' shadows a global declaration [-Wshadow]
 int hubDistance(int N, int sub) {
                               ^
towns.cpp:18:11: note: shadowed declaration is here
 const int N = 256;
           ^
towns.cpp:91:12: warning: conversion to 'unsigned int' from 'time_t {aka long int}' may alter its value [-Wconversion]
  srand(time(0));
        ~~~~^~~
towns.cpp:89:28: warning: unused parameter 'sub' [-Wunused-parameter]
 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