| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 669926 | alvingogo | Towns (IOI15_towns) | C++14 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
//#include <towns.h>
#pragma GCC optimize("Ofast")
#define AquA cin.tie(0);ios_base::sync_with_stdio(0);
#define fs first
#define sc second
#define p_q priority_queue
using namespace std;
int nn;
vector<vector<int> > dis;
int getDistance(int x,int y){
assert(x>=0 && x<nn);
assert(y>=0 && y<nn);
return dis[x][y];
}
map<pair<int,int>,int> mp;
int qt=0;
int f(int x,int y){
if(x==y){
return 0;
}
if(x>y){
swap(x,y);
}
if(mp.find({x,y})!=mp.end()){
return mp[{x,y}];
}
qt++;
return mp[{x,y}]=getDistance(x,y);
}
int hubDistance(int n,int sub){
qt=0;
mp.clear();
int a=0;
for(int i=0;i<n;i++){
if(f(0,i)>f(0,a)){
a=i;
}
}
int b=a;
for(int i=0;i<n;i++){
if(f(a,i)>f(a,b)){
b=i;
}
}
assert(a!=b);
map<int,pair<int,int> > m;
int dd=f(a,0)-((f(a,0)+f(b,0)-f(a,b))/2);
m[dd].fs=max(m[dd].fs,f(a,0)-dd);
for(int i=0;i<n;i++){
if(i!=a && i!=b){
int x=min(dd,(f(a,i)-f(0,i)+f(a,0))/2);
m[x].fs=max(m[x].fs,f(i,a)-x);
}
}
vector<int> g;
int cz=0;
for(auto &h:m){
g.push_back(h.fs);
h.sc.sc=cz;
cz++;
}
int p=g.size();
vector<int> dis(p,0);
for(int i=0;i<p;i++){
dis[i]=max(dis[i],max(g[i],f(a,b)-g[i]));
for(int j=i+1;j<p;j++){
int u=g[j]-g[i];
dis[i]=max(dis[i],m[g[j]].fs+u);
dis[j]=max(dis[j],m[g[i]].fs+u);
}
}
int y=0;
for(int i=0;i<p;i++){
if(dis[i]<dis[y]){
y=i;
}
}
vector<int> dis2(n);
for(int i=0;i<n;i++){
int x=min(dd,(f(a,i)-f(0,i)+f(a,0))/2);
dis2[i]=f(a,i)-x+abs(g[y]-x);
//cout << dis2[i] << " ";
}
//cout << '\n';
//assert(qt<=3*n);
//cout << qt << endl;
int at=1;
vector<int> vis(n),pp(n);
int cnt=0,lo=0;
for(int i=0;i<n;i++){
if(cnt==0){
lo=i;
cnt++;
}
else{
if(f(lo,i)!=dis2[i]+dis2[lo]){
cnt++;
vis[i]=1;
pp[lo]++;
}
else{
cnt--;
}
}
}
int cc=0;
for(int i=0;i<n;i++){
if(!vis[i]){
int q=(f(lo,i)!=dis2[i]+dis2[lo]);
if(q){
cc+=pp[i]+1;
}
}
}
if(cc>n/2){
at=-1;
}
return dis[y]*at;
}
int main(){
cin >> nn;
dis.resize(nn,vector<int>(nn));
for(int i=0;i<nn;i++){
for(int j=0;j<nn;j++){
cin >> dis[i][j];
}
}
cout << hubDistance(nn,1) << "\n";
return 0;
}