Submission #318715

#	Time	Username	Problem	Language	Result	Execution time	Memory
318715		VROOM_VARUN	Towns (IOI15_towns)	C++14	0 / 100	1 ms	492 KiB

towns

/*
ID: varunra2
LANG: C++
TASK: towns
*/

#include<bits/stdc++.h>
#include "towns.h"
using namespace std;

#ifdef DEBUG
#include "lib/debug.h"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define debug_arr(...) \
  cerr << "[" << #__VA_ARGS__ << "]:", debug_arr(__VA_ARGS__)
#pragma GCC diagnostic ignored "-Wsign-compare"
//#pragma GCC diagnostic ignored "-Wunused-parameter"
//#pragma GCC diagnostic ignored "-Wunused-variable"
#else
#define debug(...) 42
#endif

#define EPS 1e-9
#define IN(A, B, C) assert(B <= A && A <= C)
#define INF (int)1e9
#define MEM(a, b) memset(a, (b), sizeof(a))
#define MOD 1000000007
#define MP make_pair
#define PB push_back
#define all(cont) cont.begin(), cont.end()
#define rall(cont) cont.end(), cont.begin()
#define x first
#define y second

const double PI = acos(-1.0);
typedef long long ll;
typedef long double ld;
typedef pair<int, int> PII;
typedef map<int, int> MPII;
typedef multiset<int> MSETI;
typedef set<int> SETI;
typedef set<string> SETS;
typedef vector<int> VI;
typedef vector<PII> VII;
typedef vector<VI> VVI;
typedef vector<string> VS;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define sz(x) (int)(x).size()
typedef pair<int, int> pii;
typedef vector<int> vi;
#pragma GCC diagnostic ignored "-Wsign-compare"
// util functions
int n;
// int getDistance(int i, int j) {
  // return 0;
// }

int rootdist(int d1, int d2, int dtot) {
  // d1 + d2 - 2 * dlca = dtot
  // (d1 + d2 - dtot)/2 = dlca
  assert(!((d1 + d2 + dtot)%2));
  return (d1 + d2 - dtot)/2;
}

int leafdist(int d1, int d2, int dtot) {
  // what is the dist(d1, dlca)
  // dist(d1, dlca) = d1 - rootdist(dlca)
  return d1 - rootdist(d1, d2, dtot);
}

void calc(int from, VI& d) {
  for(int i = 0; i < n; i++) {
    if(i == from) continue;
    d[i] = getDistance(from, i);
  }
}

int root;

int hubDistance(int n, int sub) {
  ::n = n;
  VI d0(n, 0), d1(n, 0), d2(n, 0);
  calc(0, d0);
  int ind1 = max_element(all(d0)) - d0.begin();
  calc(ind1, d1);
  int ind2 = max_element(all(d1)) - d1.begin();
  calc(ind2, d2);
  // now we can root the tree at ind1
  root = ind1;
  // now the center of the tree is on the path from ind1 -> ind2
  // i.e. the center of the tree is from the root -> ind2
  // that means the center is one of the ancestors of ind2, (yeah no shit sherlock)
  int ret = 2 * INF;  
  for(int i = 0; i < n; i++) {
    ret = min(ret, max(rootdist(ind2, i, d2[i]), leafdist(ind2, i, d2[i])));
  }
  return ret;
}

// int main() {
// #ifndef ONLINE_JUDGE
//   freopen("towns.in", "r", stdin);
//   freopen("towns.out", "w", stdout);
// #endif
//   cin.sync_with_stdio(0); cin.tie(0);

//   return 0;
// }

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:82:31: warning: declaration of 'n' shadows a global declaration [-Wshadow]
   82 | int hubDistance(int n, int sub) {
      |                               ^
towns.cpp:55:5: note: shadowed declaration is here
   55 | int n;
      |     ^
towns.cpp:86:35: warning: conversion from '__gnu_cxx::__normal_iterator<int*, std::vector<int> >::difference_type' {aka 'long int'} to 'int' may change value [-Wconversion]
   86 |   int ind1 = max_element(all(d0)) - d0.begin();
      |              ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
towns.cpp:88:35: warning: conversion from '__gnu_cxx::__normal_iterator<int*, std::vector<int> >::difference_type' {aka 'long int'} to 'int' may change value [-Wconversion]
   88 |   int ind2 = max_element(all(d1)) - d1.begin();
      |              ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
towns.cpp:82:28: warning: unused parameter 'sub' [-Wunused-parameter]
   82 | int hubDistance(int n, int sub) {
      |                        ~~~~^~~

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