Problem p02347 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cstdio>
#include <vector>

using namespace std;

struct Point {
  int id, x, y;

  bool operator<(const Point &right) { return id < right.id; }
};

struct Node {
  int location, l, r;
};

bool LESS_X(const Point &left, const Point &right) { return left.x < right.x; }

bool LESS_Y(const Point &left, const Point &right) { return left.y < right.y; }

const int MAX = 500000;
int NIL = -1;

Point P[MAX];
Node T[MAX];
vector<Point> ans;

void find(int v, int sx, int tx, int sy, int ty, int depth) {
  int x = P[T[v].location].x;
  int y = P[T[v].location].y;

  if (sx <= x && x <= tx && sy <= y && y <= ty)
    ans.push_back(P[T[v].location]);

  if (depth % 2 == 0) {
    if (T[v].l != NIL) {
      if (sx <= x) {
        find(T[v].l, sx, tx, sy, ty, depth + 1);
      }
    }
    if (T[v].r != NIL) {
      if (x <= tx) {
        find(T[v].r, sx, tx, sy, ty, depth + 1);
      }
    }
  } else {
    if (T[v].l != NIL) {
      if (sy <= y) {
        find(T[v].l, sx, tx, sy, ty, depth + 1);
      }
    }
    if (T[v].r != NIL) {
      if (y <= ty) {
        find(T[v].r, sx, tx, sy, ty, depth + 1);
      }
    }
  }
}

int np = 0;
int makeKdTree(int l, int r, int depth) {
  if (!(l < r))
    return NIL;

  int t = np++;
  int mid = (l + r) / 2;
  T[t].location = mid;

  if (depth % 2 == 0) {
    sort(P + l, P + r, LESS_X);
  } else {
    sort(P + l, P + r, LESS_Y);
  }

  T[t].l = makeKdTree(l, mid, depth + 1);
  T[t].r = makeKdTree(mid + 1, r, depth + 1);

  return t;
}

int main() {

  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; ++i) {
    int x, y;
    scanf("%d %d", &x, &y);

    Point point;
    point.id = i;
    point.x = x;
    point.y = y;
    P[i] = point;

    Node node;
    node.location = node.l = node.r = NIL;
    T[i] = node;
  }

  makeKdTree(0, n, 0);

  int q;
  scanf("%d", &q);
  for (int i = 0; i < q; ++i) {
    int sx, tx, sy, ty;
    scanf("%d %d %d %d", &sx, &tx, &sy, &ty);

    ans.clear();
    find(0, sx, tx, sy, ty, 0);
    sort(ans.begin(), ans.end());
    for (int j = 0; j < (int)ans.size(); ++j) {
      printf("%d\\n", ans[j].id);
    }
    printf("\\n");
  }

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cstdio>
#include <iostream>
#include <vector>

using namespace std;

struct Point {
  int id, x, y;

  bool operator<(const Point &right) { return id < right.id; }
};

struct Node {
  int location, l, r;
};

bool LESS_X(const Point &left, const Point &right) { return left.x < right.x; }

bool LESS_Y(const Point &left, const Point &right) { return left.y < right.y; }

const int MAX = 500000;
int NIL = -1;

Point P[MAX];
Node T[MAX];
vector<Point> ans;

void find(int v, int sx, int tx, int sy, int ty, int depth) {
  int x = P[T[v].location].x;
  int y = P[T[v].location].y;

  if (sx <= x && x <= tx && sy <= y && y <= ty)
    ans.push_back(P[T[v].location]);

  if (depth % 2 == 0) {
    if (T[v].l != NIL) {
      if (sx <= x) {
        find(T[v].l, sx, tx, sy, ty, depth + 1);
      }
    }
    if (T[v].r != NIL) {
      if (x <= tx) {
        find(T[v].r, sx, tx, sy, ty, depth + 1);
      }
    }
  } else {
    if (T[v].l != NIL) {
      if (sy <= y) {
        find(T[v].l, sx, tx, sy, ty, depth + 1);
      }
    }
    if (T[v].r != NIL) {
      if (y <= ty) {
        find(T[v].r, sx, tx, sy, ty, depth + 1);
      }
    }
  }
}

int np = 0;
int makeKdTree(int l, int r, int depth) {
  if (!(l < r))
    return NIL;

  int t = np++;
  int mid = (l + r) / 2;
  T[t].location = mid;

  if (depth % 2 == 0) {
    sort(P + l, P + r, LESS_X);
  } else {
    sort(P + l, P + r, LESS_Y);
  }

  T[t].l = makeKdTree(l, mid, depth + 1);
  T[t].r = makeKdTree(mid + 1, r, depth + 1);

  return t;
}

int main() {

  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; ++i) {
    int x, y;
    scanf("%d %d", &x, &y);

    Point point;
    point.id = i;
    point.x = x;
    point.y = y;
    P[i] = point;

    Node node;
    node.location = node.l = node.r = NIL;
    T[i] = node;
  }

  makeKdTree(0, n, 0);

  int q;
  scanf("%d", &q);
  for (int i = 0; i < q; ++i) {
    int sx, tx, sy, ty;
    scanf("%d %d %d %d", &sx, &tx, &sy, &ty);

    ans.clear();
    find(0, sx, tx, sy, ty, 0);
    sort(ans.begin(), ans.end());
    for (int j = 0; j < (int)ans.size(); ++j) {
      cout << ans[j].id << endl;
    }
    cout << endl;
  }

  return 0;
}