HackerRank - Point Filtering study code #12

PointFiltering_studyCode12.cpp

#include <cmath>
#include <cstdio>
#include <vector>
#include <map>
#include <iostream>
#include <algorithm>
#include <tuple>
#include <iomanip>
using namespace std;

struct Item {
  size_t id;
  double x, y, z;
  Item() : id(0), x(0), y(0), z(0) {}
  Item(size_t id, double x, double y, double z) : id(id), x(x), y(y), z(z) {}
};


ostream& operator <<(ostream& os, const Item& item)
{ return os << item.id << " " << item.x << " " << item.y << " " << item.z; }

int main() {
  string s;
  size_t n, b;
  getline(cin >> n >> b, s);
  vector<Item> mainList;
  for (size_t i = 0; i < n; ++i) {
    size_t id;
    double x, y, z;
    getline(cin >> id >> x >> y >> z, s);
    mainList.emplace_back(id, x, y, z);
  }
  
  map<size_t, Item> bucket;
  sort(mainList.begin(), mainList.end(), 
       [](const Item& a, const Item&b) { return a.z < b.z; });
  for (auto it = mainList.end()-b; it != mainList.end(); ++it)
    bucket[it->id] = *it;
  mainList.resize(mainList.size() - b);
  
  string cmd;
  size_t k;
  while (cin >> cmd >> k) {
    if (cmd == "F" || cmd == "f") {
      if (bucket.count(k)) {
        const Item& item = bucket[k];
        cout << k << " = (" << fixed << setprecision(3) << item.x << "," << item.y << "," << item.z << ")" << endl;
      }
      else
        cout << "Point doesn't exist in the bucket." << endl;
    }
    else if (cmd == "R" || cmd == "r") {
      if (bucket.count(k)) {
        if (mainList.size()) {
          bucket.erase(k);
          const Item& item = mainList.back();
          bucket[item.id] = item;
          mainList.resize(mainList.size() - 1);
          cout << "Point id " << k << " removed." << endl;
        }
        else
          cout << "No more points can be deleted." << endl;
      }
      else
        cout << "Point doesn't exist in the bucket." << endl;
    }
    getline(cin, s);
  }
  return 0;
}