Submission #887661

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
887661	2023-12-15T01:20:01 Z	ad_red	Tri (CEOI09_tri)	C++17	0 / 100	57 ms	13432 KB

#include <bits/stdc++.h>
#define endl "\n"

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

using namespace std;
using ll = long long;
using ld = long double;

ll inf = 1e9;

struct Point{
  ll x, y;
};

void pv(vector<Point> s) {
  for (auto c : s) {
    cout << "{" << c.x << ", " << c.y << "} ";
  }
  cout << endl;
}

ll vp(Point a, Point b) {
  return a.x * b.y - a.y * b.x;
}

ll sgn(Point a, Point b, Point c) {
  // -1 if the order is A-B-C from left to right if B is the bottom point
  // 1 or 0 otherwise

  ll q = vp(Point{a.x - b.x, a.y - b.y}, Point{c.x - b.x, c.y - b.y});
  return (q / abs(q));
}

bool operator<(Point a, Point b) {
  return sgn(a, Point{0LL, 0LL}, b) == -1;
}

bool in_triangle(Point a, Point b, Point c, Point p) {
  // assuming A-B-C

  return (sgn(a, b, p) == -1 && sgn(c, b, p) == 1 && sgn(p, c, a) == -1);
}

bool cmp_hull(Point a, Point b) {
  if (a.x == b.x) return a.y < b.y;
  return a.x < b.x;
}

/*
  Plan:
  0. Sort all points by angle
  1. Construct sqrt(n) convex hulls for all point sets
  2. For each triangle, consider all sqrt(n) ranges of points already present
  3. Check all points that are outside of the hulls manually
  3.5 On both sides
  4. For each complete range with a hull do a binary search on that hull:
  5. Start with the leftmost (by the angle) point, end with the point anticlockwise on the convex hull
  6. Check if the mid is in the triangle, if it is, then break. If we are moving further from the triangle by choosing a point to the right of the current one (cur_mid), then r = mid, else l = mid.

  Claim: the total thing takes no more than 200 lines.
*/

vector<Point> points;
const ll sqrt_size = 600;

int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);

  ll n, m;
  cin >> n >> m;

  for (int i = 0; i < n; i++) {
    ll x, y;
    cin >> x >> y;

    points.push_back(Point{x, y});
  }

  sort(points.begin(), points.end()); // the comparator is there

  vector<vector<Point>> hulls(n);

  for (int i = 0; i < n; i++) {
    hulls[i / sqrt_size].push_back(points[i]);
  }


  for (int i = 0; i < n; i++) {
    if (hulls[i].empty()) continue;
    
    vector<Point> hull;

    sort(hulls[i].begin(), hulls[i].end(), cmp_hull);


    for (auto p : hulls[i]) {
      while (hull.size() > 1 && sgn(p, hull[(int)hull.size() - 2], hull.back()) == -1) {
        hull.pop_back();
      }
      hull.push_back(p);
    }

    hulls[i] = hull;
    // top convex hull only!
  }

  // end of hull processing

  for (int trn = 0; trn < m; trn++) {
    // current triangle

    Point a, b;
    cin >> a.x >> a.y >> b.x >> b.y;

    if (sgn(a, Point{0LL, 0LL}, b) == 1) swap(a, b);

    ll left_start, right_end;

    // left_start - leftmost point that is in the angle
    // right_end - leftmost point after the angle

    ll l = -1;
    ll r = n - 1;

    while (r - l > 1) {
      ll mid = (l + r) / 2;
      if (sgn(a, Point{0, 0}, points[mid]) >= 0) {
        l = mid;
      } else {
        r = mid;
      }
    }

    left_start = r;

    l = 0;
    r = n;

    while (r - l > 1) {
      ll mid = (l + r) / 2;
      if (sgn(b, Point{0, 0}, points[mid]) >= 0) {
        l = mid;
      } else {
        r = mid;
      }
    }

    right_end = r;

    if (l >= r) {
      cout << "N" << endl;
      continue;
    }

    bool flag = false;

    if (right_end - left_start < sqrt_size) {
      for (int i = left_start; i < right_end; i++) {
        if (in_triangle(a, Point{0, 0}, b, points[i])) {
          flag = true;
          break;
        }
      }

      if (flag) {
        cout << "Y" << endl;
      } else {
        cout << "N" << endl;
      }

      continue;
    }

    flag = false;

    while (left_start < right_end && left_start % sqrt_size != 0) {
      if (in_triangle(a, Point{0, 0}, b, points[left_start])) {
        flag = true;
        break;
      }
      left_start++;
    }


    while (right_end > left_start && right_end % sqrt_size != 0) {
      right_end--;
      if (in_triangle(a, Point{0, 0}, b, points[right_end])) {
        flag = true;
        break;
      }
    }

    if (right_end <= left_start) {
      if (flag) {
        cout << "Y" << endl;
      } else {
        cout << "N" << endl;
      }
      continue;
    }

    assert(left_start % sqrt_size == 0);
    assert(right_end % sqrt_size == 0);

    if (flag) {
      cout << "Y" << endl;
      continue;
    }

    
    flag = false;

    for (int i = left_start / sqrt_size; i < right_end / sqrt_size; i++) {
      // convex hull processing

      ll l = 0;
      ll r = (int)hulls[i].size();

      while (r - l > 1) {
        ll mid = (r + l) / 2;

        if (in_triangle(a, Point{0, 0}, b, hulls[i][mid])) {
          flag = true;
          break;
        }

        if (mid + 1 == hulls[i].size() || !in_triangle(a, Point{0, 0}, b, hulls[i][mid + 1]) && sgn(hulls[i][mid + 1], a, hulls[i][mid]) == -1) {
          r = mid;
        } else {
          l = mid;
        }
      }

      for (int j = (l - 3 + hulls[i].size()) % hulls[i].size(); j <= (r + 3 + hulls[i].size()) % hulls[i].size(); j++) {
        if (in_triangle(a, Point{0, 0}, b, hulls[i][j])) {
          flag = true;
          break;
        }
      }

      if (flag) break;
    }

    if (flag) {
      cout << "Y" << endl;
    } else {
      cout << "N" << endl;
    }
  }

  return 0;
}

Compilation message

tri.cpp: In function 'int main()':
tri.cpp:230:21: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<Point>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  230 |         if (mid + 1 == hulls[i].size() || !in_triangle(a, Point{0, 0}, b, hulls[i][mid + 1]) && sgn(hulls[i][mid + 1], a, hulls[i][mid]) == -1) {
      |             ~~~~~~~~^~~~~~~~~~~~~~~~~~
tri.cpp:230:94: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
  230 |         if (mid + 1 == hulls[i].size() || !in_triangle(a, Point{0, 0}, b, hulls[i][mid + 1]) && sgn(hulls[i][mid + 1], a, hulls[i][mid]) == -1) {
      |                                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tri.cpp:237:67: warning: comparison of integer expressions of different signedness: 'int' and 'long long unsigned int' [-Wsign-compare]
  237 |       for (int j = (l - 3 + hulls[i].size()) % hulls[i].size(); j <= (r + 3 + hulls[i].size()) % hulls[i].size(); j++) {
      |                                                                 ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
0 / 100.0

#	Verdict	Execution time	Memory	Grader output
1	Runtime error	1 ms	604 KB	Execution killed with signal 6
2	Runtime error	1 ms	604 KB	Execution killed with signal 6
3	Incorrect	57 ms	2516 KB	Output isn't correct
4	Runtime error	18 ms	7128 KB	Execution killed with signal 6
5	Runtime error	39 ms	13432 KB	Execution killed with signal 6
6	Runtime error	24 ms	11024 KB	Execution killed with signal 6
7	Runtime error	30 ms	13336 KB	Execution killed with signal 6
8	Runtime error	29 ms	10964 KB	Execution killed with signal 6
9	Runtime error	33 ms	12084 KB	Execution killed with signal 6
10	Runtime error	34 ms	13220 KB	Execution killed with signal 6

Submission #887661

Compilation message

Subtask #1 0 / 100.0

Subtask #1
0 / 100.0