Submission #1072734

#	Time	Username	Problem	Language	Result	Execution time	Memory
1072734		PenguinsAreCute	Building Skyscrapers (CEOI19_skyscrapers)	C++17	0 / 100	100 ms	12752 KiB

skyscrapers

#include <bits/stdc++.h>
using namespace std;
using i2 = pair<int,int>;
#define fi first
#define se second
#define lb lower_bound
#define ub upper_bound
#define all(v) begin(v),end(v)
#define sz(v) int(v.size())
vector<int> vadj[150005];
int dist[150005];
void bfs(int s) {
  queue<int> q;
  dist[s]=0;
  for(q.push(s);q.size();) {
    int x = q.front(); q.pop();
    for(auto i: vadj[x]) if(dist[i]==-1) {
      dist[i]=dist[x]+1;
      q.push(i);
    }
  }
}
struct block {int x, y, i;};
vector<int> build_skyscrapers(int t, vector<int> r, vector<int> c) {
  int n = r.size();
  block lst[n];
  for(int i=0;i<n;i++) lst[i]={r[i],c[i],i};
  auto lamb = [](block a, block b){return i2(a.x,a.y)<i2(b.x,b.y);};
  sort(lst,lst+n,lamb);
  int dx[8]={-1,-1,-1,0,0,1,1,1}, dy[8]={-1,0,1,-1,1,-1,0,1};
  vector<int> eadj[n]; int edeg[n]; fill(edeg,edeg+n,0);
  for(int i=0;i<n;i++) for(int j=0;j<8;j++) {
    auto it=lb(lst,lst+n,block{r[i]+dx[j],c[i]+dy[j],0},lamb);
    if(it!=lst+n&&(*it).x==r[i]+dx[j]&&(*it).y==c[i]+dy[j]) {
      vadj[i].push_back((*it).i);
      if(i==1||i==3||i==4||i==6) eadj[i].push_back((*it).i), edeg[i]++;
    }
  }
  fill(dist,dist+n,-1);
  bfs(0);
  if(*min_element(dist,dist+n)==-1) return {-1};
  priority_queue<i2> pq;
  for(int i=0;i<n;i++) if(edeg[i]<4) pq.push({dist[i],i});
  vector<int> perm;
  while(pq.size()) {
    int x = pq.top().second; pq.pop();
    perm.push_back(x);
    for(auto i: eadj[x]) if(edeg[i]==4) {
      edeg[i]=3;
      pq.push({dist[i],i});
    }
  }
  reverse(perm.begin(),perm.end());
  return perm;
}

// grader
main() {
  int n, t;
  assert(2==scanf("%d %d",&n,&t));
  vector<int> r(n), c(n);
  for(int i=0;i<n;i++) assert(2==scanf("%d %d",&r[i],&c[i]));
  vector<int> v = build_skyscrapers(t,r,c);
  if(v[0]==-1) printf("NO");
  else {
    printf("YES\n");
    for(auto i: v) printf("%d\n",i+1);
  }
}

/*

Find node furthest away?
furthest node may be in center.
Find skyscraper edge furthest away among all exposed skyscrapers.
remove it.
repeat.
(furthest from arbitrary node)
*/

Compilation message (stderr)

skyscrapers.cpp:58:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   58 | main() {
      | ^~~~

• Subtask 1: 0 / 8
• Subtask 2: 0 / 14
• Subtask 3: 0 / 12
• Subtask 4: 0 / 17
• Subtask 5: 0 / 20
• Subtask 6: 0 / 10
• Subtask 7: 0 / 19