| # |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
| 51961 |
2018-06-22T18:31:39 Z |
kingpig9 |
Towns (IOI15_towns) |
C++11 |
|
24 ms |
720 KB |
#include <bits/stdc++.h>
#include "towns.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int MAXN = 115;
const int INF = 1e9;
#define debug(...) fprintf(stderr, __VA_ARGS__)
//#define debug(...)
#define fi first
#define se second
#define all(v) (v).begin(), (v).end()
#define fillchar(a, s) memset((a), (s), sizeof(a))
#warning There can be more than one test case. Make sure you reset at every level.
template<class T>
void setmin (T &a, T b) {
if (b < a) {
a = b;
}
}
template<class T>
void setmax (T &a, T b) {
if (a < b) {
a = b;
}
}
int N;
int subtask;
int dist[MAXN][MAXN];
int getdist (int x, int y) {
assert(0 <= x);
assert(x < N);
assert(0 <= y);
assert(y < N);
if (x == y) {
return 0;
}
if (x > y) {
swap(x, y);
}
int &ref = dist[x][y];
if (ref) {
return ref;
}
return ref = getDistance(x, y);
}
array<int, 3> getcent (int a, int b, int c) {
//get distance to the meeting place of a, b, c
int dab = getdist(a, b), dac = getdist(a, c), dbc = getdist(b, c);
return array<int, 3> {(dab + dac - dbc) / 2, (dab - dac + dbc) / 2, (-dab + dac + dbc) / 2};
}
pii getfar (int x) {
//farthest away
pii res(0, x);
for (int i = 0; i < N; i++) {
setmax(res, pii(getdist(i, x), i));
}
return res;
}
pair<int, pii> getdiam() {
int diamx = getfar(0).se;
pii farx = getfar(diamx);
return make_pair(farx.fi, pii(diamx, farx.se));
}
int diamx, diamy, diam;
int ans;
map<int, vector<int>> mp;
map<int, int> psum, ssum; //prefix sum, suffix sum
void reset() {
fillchar(dist, 0);
diamx = diamy = diam = ans = 0;
mp.clear();
psum.clear();
ssum.clear();
}
bool has_balanced_hub() {
for (auto it : mp) {
//check if hub
int dl = it.fi, dr = diam - dl;
if (dl == 0 || dr == 0) {
continue;
}
if (max(dl, dr) == ans) {
//this is a hub
auto pit = prev(psum.find(dl));
auto sit = next(ssum.find(dl));
int lsize = pit->se;
int rsize = sit->se;
//debug("dl = %d, dr = %d. lsize = %d, rsize = %d. csize = %d.\n", dl, dr, lsize, rsize, csize);
if (lsize > N / 2 || rsize > N / 2) {
continue;
}
vector<int> leaves = it.se;
int csize = leaves.size();
if (csize <= N / 2) {
return true;
}
if (subtask == 4) {
//solves subtask 4 -- don't need to check anything else.
continue;
}
//dumb asserts -- primarily for reassurance
assert(lsize <= N / 2);
assert(rsize <= N / 2);
assert(csize > N / 2);
//otherwise - majority element!
vector<int> vlist, bucket;
for (int leaf : leaves) {
if (vlist.empty() || getcent(diamx, vlist.back(), leaf)[0] == dl) {
//not equal
vlist.push_back(leaf);
if (!bucket.empty()) {
vlist.push_back(bucket.back());
bucket.pop_back();
}
} else {
//equal
bucket.push_back(leaf);
}
}
//check now whether it is a majority element
//More formally: "maj" = potential majority element. Nothing else could be a majority element. Check its count.
int maj = vlist.back(); //majority element
while (!vlist.empty()) {
int leaf = vlist.back();
if (getcent(diamx, maj, leaf)[0] == dl) {
//not equal
if (bucket.empty()) {
return true;
}
bucket.pop_back();
vlist.pop_back();
} else {
//equal
if (vlist.size() == 1) {
bucket.push_back(vlist[0]);
vlist.pop_back();
} else {
vlist.pop_back();
vlist.pop_back();
}
}
}
if (bucket.empty()) {
return true;
}
}
}
return false;
}
int go() {
pair<int, pii> diamdata = getdiam();
diamx = diamdata.se.fi;
diamy = diamdata.se.se;
diam = diamdata.fi;
//debug("diameter: %d -> %d, distance %d\n", diamx, diamy, diam);
ans = INF;
mp = {{0, {diamx}}, {diam, {diamy}}};
for (int i = 0; i < N; i++) {
if (i != diamx && i != diamy) {
auto cen = getcent(i, diamx, diamy);
int fardist = max(cen[1], cen[2]);
//debug("i = %d. fardist = %d\n", i, fardist);
assert(fardist == max({cen[0], cen[1], cen[2]}));
setmin(ans, fardist);
assert(cen[1] + cen[2] == diam);
mp[cen[1]].push_back(i);
}
}
if (subtask <= 2) {
//no need for balanced hub - solves subtasks 1 and 2
return ans;
}
for (auto it = mp.begin(); it != mp.end(); it++) {
psum[it->fi] = it->se.size();
if (it != mp.begin()) {
psum[it->fi] += psum[prev(it)->fi];
}
}
for (auto it = mp.rbegin(); it != mp.rend(); it++) {
ssum[it->fi] = it->se.size();
if (it != mp.rbegin()) {
ssum[it->fi] += ssum[prev(it)->fi];
}
}
return has_balanced_hub() ? ans : -ans;
}
int hubDistance (int nnn, int subbbb) {
#warning reset totally global variables
N = nnn;
subtask = subbbb;
reset();
return go();
}
Compilation message
towns.cpp:18:2: warning: #warning There can be more than one test case. Make sure you reset at every level. [-Wcpp]
#warning There can be more than one test case. Make sure you reset at every level.
^~~~~~~
towns.cpp:223:2: warning: #warning reset totally global variables [-Wcpp]
#warning reset totally global variables
^~~~~~~
towns.cpp: In function 'bool has_balanced_hub()':
towns.cpp:114:27: warning: conversion to 'int' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Wconversion]
int csize = leaves.size();
~~~~~~~~~~~^~
towns.cpp: In function 'int go()':
towns.cpp:207:29: warning: conversion to 'std::map<int, int>::mapped_type {aka int}' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Wconversion]
psum[it->fi] = it->se.size();
~~~~~~~~~~~^~
towns.cpp:213:29: warning: conversion to 'std::map<int, int>::mapped_type {aka int}' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Wconversion]
ssum[it->fi] = it->se.size();
~~~~~~~~~~~^~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
20 ms |
376 KB |
Output is correct |
| 2 |
Correct |
17 ms |
612 KB |
Output is correct |
| 3 |
Correct |
2 ms |
612 KB |
Output is correct |
| 4 |
Correct |
22 ms |
612 KB |
Output is correct |
| 5 |
Correct |
22 ms |
612 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
20 ms |
620 KB |
Output is correct |
| 2 |
Correct |
17 ms |
672 KB |
Output is correct |
| 3 |
Correct |
22 ms |
720 KB |
Output is correct |
| 4 |
Correct |
24 ms |
720 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
17 ms |
720 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
22 ms |
720 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
17 ms |
720 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
2 ms |
720 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
