Submission #601205

#	Time	Username	Problem	Language	Result	Execution time	Memory
601205		MilosMilutinovic	분수 공원 (IOI21_parks)	C++17	5 / 100	571 ms	39768 KiB

parks

/**
 *    author:  wxhtzdy
 *    created: 21.07.2022 14:34:57
**/
/* 
  First idea was 2SAT having verteces (road, direction), but there always exist constructive idea...
  https://oj.uz/submission/437652 
*/
#include "parks.h"
#include <bits/stdc++.h>

using namespace std;

const int dx[] = {2, 0, -2, 0};
const int dy[] = {0, 2, 0, -2};

class dsu {
  public:
  vector<int> p;
  int n;
  dsu(int _n) : n(_n) {
    p.resize(n);
    iota(p.begin(), p.end(), 0);
  }
  inline int get(int x) {
    return (x == p[x] ? x : (p[x] = get(p[x])));
  }
  inline bool unite(int x, int y) {
    x = get(x);
    y = get(y);
    if (x != y) {
      p[x] = y;
      return true;
    }
    return false;
  }
};

int construct_roads(vector<int> x, vector<int> y) {
  int n = (int) x.size();
  map<pair<int, int>, int> mp;
  for (int i = 0; i < n; i++) {
    mp[{x[i], y[i]}] = i;
  }
  vector<vector<int>> id(n, vector<int>(4, -1));
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < 4; j++) {
      int nx = x[i] + dx[j];
      int ny = y[i] + dy[j];
      if (mp.count({nx, ny})) {
        id[i][j] = mp[{nx, ny}];        
      }
    }
  }
  dsu d(n);
  vector<int> u, v;
  vector<int> a, b;
  auto Add = [&](int i, int j) {
    d.unite(i, j);
    u.push_back(i);
    v.push_back(j);
    if (x[i] == x[j]) {
      b.push_back(y[i] + y[j] >> 1);
      if ((x[i] + y[i]) % 2 == 1) {
        a.push_back(x[i] - 1);
      } else {
        a.push_back(x[i] + 1);
      }
    } else {
      a.push_back(x[i] + x[j] >> 1);
      if ((x[i] + y[i]) % 2 == 1) {
        b.push_back(y[i] + 1);
      } else {
        b.push_back(y[i] - 1);
      }
    }
  };
  for (int i = 0; i < n; i++) {
    int i0 = id[i][0], i1 = id[i][1];
    if (i0 == -1 && i1 == -1) {
      continue;
    }
    if (i0 == -1) {
      Add(i, i1);
      continue;
    }
    if (i1 == -1) {
      Add(i, i0);
      continue;
    }
    if (d.get(i0) != d.get(i1)) {
      Add(i, i0);
      Add(i, i1);
    } else {
      if ((x[i] + y[i]) % 2 == 1) {
        Add(i, i0);
      } else {
        Add(i, i1);
      }
    }
  }
  if ((int) u.size() != n - 1) {
    return 0;    
  }
  build(u, v, a, b);
  return 1;
}

Compilation message (stderr)

parks.cpp: In lambda function:
parks.cpp:63:24: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   63 |       b.push_back(y[i] + y[j] >> 1);
parks.cpp:70:24: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   70 |       a.push_back(x[i] + x[j] >> 1);

• Subtask 1: 5 / 5
• Subtask 2: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 20
• Subtask 5: 0 / 20
• Subtask 6: 0 / 30