| # |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
| 319140 |
2020-11-04T04:09:51 Z |
VROOM_VARUN |
Towns (IOI15_towns) |
C++14 |
|
23 ms |
1012 KB |
/*
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;
const int mx = 150;
int vals[mx][mx];
map<PII, int> mp;
int qrys = 0;
// int getDistance(int i, int j) { return vals[i][j]; }
int gt(int i, int j) {
if (i > j) swap(i, j);
if (i == j) return 0;
if (mp[MP(i, j)]) return mp[MP(i, j)];
mp[MP(i, j)] = getDistance(i, j);
qrys++;
return mp[MP(i, j)];
}
int rootdist(int d1, int d2, int dtot) {
// d1 + d2 - 2 * dlca = dtot
// (d1 + d2 - dtot)/2 = dlca
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] = gt(from, i);
}
}
int ind1;
int ind2;
VI d0;
VI d1;
VI d2; // we won't be using this
VI lcadists;
void init() {
mp.clear();
d0.clear();
d1.clear();
d2.clear();
lcadists.clear();
d0.assign(n, 0);
d1.assign(n, 0);
d2.assign(n, 0);
lcadists.assign(n, 0);
qrys = 0;
}
int find(int lcdist) {
int val1 = d0[ind1] - lcdist;
int val2 = d1[ind2] - val1;
int cur = max(val1, val2);
return cur;
}
VI cop;
int radius;
VI findHubs() {
// we will use 2n - 3 queries to find the hubs/radius/center
calc(0, d0);
ind1 = max_element(all(d0)) - d0.begin();
calc(ind1, d1);
ind2 = max_element(all(d1)) - d1.begin();
// good till
// diameter is from ind1 -> ind2
// hub lies on the path from 0 -> ind1 && ind1 -> ind2
// so since we rooted the tree at 0
// the hub lies on the path from ind1 -> lca(ind1, ind2)
int ret = 2 * INF;
VI hubs;
// sort(all(lcadists));
for (int i = 0; i < n; i++) {
// lcadists actually holds distance from ind1 -> lca(ind1, i)
lcadists[i] = leafdist(d0[ind1], d0[i], d1[i]);
int cur = max(lcadists[i], d1[ind2] - lcadists[i]);
if (cur < ret) {
ret = cur;
hubs.clear();
hubs = {i};
} else if (cur == ret and lcadists[i] != lcadists[hubs[0]]) {
hubs.PB(i);
}
}
radius = ret;
hubs.resize(2);
return hubs;
}
int ccnt(int dep) {
int ret = 0;
for (auto& x : cop) {
if (x >= dep) ret++;
}
return ret;
}
int chk;
bool same(int i, int j) {
if (lcadists[i] < chk and lcadists[j] < chk)
return true; // same children subtree
if (lcadists[i] > chk and lcadists[j] > chk)
return true; // outside hub subtree
if (lcadists[i] == chk and lcadists[j] == chk) { // same subtree
if (d1[i] + d1[j] - gt(i, j) > 2 * chk) return true;
}
return false;
}
bool balanced(int depth) {
// debug(depth);
chk = depth;
// we need to check if an array contains a majority using (3n/2 - 2) checks
// http://www.cs.yale.edu/publications/techreports/tr252.pdf
// ^ paper describes how to do it
VI bucket;
VI list;
// phase 1
for (int i = 0; i < n; i++) {
if (list.empty())
list.PB(i);
else if (same(list.back(), i))
bucket.PB(i);
else {
list.PB(i);
if (!bucket.empty()) {
list.PB(bucket.back());
bucket.pop_back();
}
}
}
// debug(bucket);
// debug(list);
// phase 2
int T = list.back();
while (!list.empty()) {
int last = list.back();
list.pop_back();
if (same(last, T)) {
if (list.empty()) {
bucket.PB(last);
} else
list.pop_back();
} else {
if (bucket.empty()) return true;
bucket.pop_back();
}
}
// impa fan :yay:
// debug(bucket);
return bucket.empty();
}
int hubDistance(int n, int sub) {
::n = n;
init();
auto hubs = findHubs();
int hubcheck;
// for(auto& x: hubs) {
// if(balanced(lcadists[x])) return radius;
// }
// return -radius;
if (sz(hubs) == 1) {
hubcheck = hubs[0];
}
// debug(lcadists);
int ind = 0;
int cnt = 0;
if (sz(hubs) == 2) {
if (lcadists[hubs[0]] > lcadists[hubs[1]]) swap(hubs[1], hubs[0]);
// we need to count how many leafs are in the subtree of hubs[0]
for (int i = 0; i < n; i++) {
if (lcadists[i] <= lcadists[hubs[0]]) cnt++;
}
// if ((n - cnt) > n / 2)
// hubcheck = hubs[1], ind = 1;
// else
// hubcheck = hubs[0];
if (cnt == n / 2) {
return radius;
}
if (cnt > n / 2) {
hubcheck = hubs[0];
} else
hubcheck = hubs[1], ind = 1;
}
// debug(hubs);
// debug(lcadists);
// debug(ind1);
// debug(lcadists[ind1]);
// debug(lcadists[0]);
if (balanced(lcadists[hubcheck])) return radius;
// if (sz(hubs) == 1) return -radius;
// if (balanced(lcadists[hubs[ind ^ 1]])) {
// debug(cnt);
// debug(n);
// debug(n - cnt);
// debug(n / 2);
// debug(ind);
// }
return -radius;
}
// int main() {
// #ifndef ONLINE_JUDGE
// freopen("towns.in", "r", stdin);
// freopen("towns.out", "w", stdout);
// #endif
// cin.sync_with_stdio(0);
// cin.tie(0);
// int subbb;
// cin >> subbb;
// int t;
// cin >> t;
// while (t--) {
// int n;
// cin >> n;
// for (int i = 0; i < n; i++) {
// for (int j = 0; j < n; j++) {
// cin >> vals[i][j];
// }
// }
// cout << hubDistance(n, 2) << '\n';
// }
// return 0;
// }
Compilation message
towns.cpp: In function 'VI findHubs()':
towns.cpp:128:31: warning: conversion from '__gnu_cxx::__normal_iterator<int*, std::vector<int> >::difference_type' {aka 'long int'} to 'int' may change value [-Wconversion]
128 | ind1 = max_element(all(d0)) - d0.begin();
| ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
towns.cpp:130:31: warning: conversion from '__gnu_cxx::__normal_iterator<int*, std::vector<int> >::difference_type' {aka 'long int'} to 'int' may change value [-Wconversion]
130 | ind2 = max_element(all(d1)) - d1.begin();
| ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:230:31: warning: declaration of 'n' shadows a global declaration [-Wshadow]
230 | int hubDistance(int n, int sub) {
| ^
towns.cpp:56:5: note: shadowed declaration is here
56 | int n;
| ^
towns.cpp:248:7: warning: variable 'ind' set but not used [-Wunused-but-set-variable]
248 | int ind = 0;
| ^~~
towns.cpp:230:28: warning: unused parameter 'sub' [-Wunused-parameter]
230 | int hubDistance(int n, int sub) {
| ~~~~^~~
towns.cpp:275:33: warning: 'hubcheck' may be used uninitialized in this function [-Wmaybe-uninitialized]
275 | if (balanced(lcadists[hubcheck])) return radius;
| ^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
19 ms |
1004 KB |
Output is correct |
| 2 |
Correct |
16 ms |
876 KB |
Output is correct |
| 3 |
Correct |
1 ms |
364 KB |
Output is correct |
| 4 |
Correct |
22 ms |
876 KB |
Output is correct |
| 5 |
Correct |
22 ms |
876 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
19 ms |
1004 KB |
Output is correct |
| 2 |
Correct |
16 ms |
896 KB |
Output is correct |
| 3 |
Correct |
22 ms |
876 KB |
Output is correct |
| 4 |
Correct |
22 ms |
1012 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
16 ms |
876 KB |
Output is correct |
| 2 |
Correct |
22 ms |
996 KB |
Output is correct |
| 3 |
Correct |
1 ms |
364 KB |
Output is correct |
| 4 |
Correct |
22 ms |
1004 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
20 ms |
1004 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
17 ms |
876 KB |
Output is correct |
| 2 |
Correct |
22 ms |
1004 KB |
Output is correct |
| 3 |
Correct |
22 ms |
876 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
16 ms |
876 KB |
Output is correct |
| 2 |
Correct |
22 ms |
896 KB |
Output is correct |
| 3 |
Correct |
23 ms |
996 KB |
Output is correct |
