Submission #888592

#	Time	Username	Problem	Language	Result	Execution time	Memory
888592		ad_red	Tri (CEOI09_tri)	C++17	10 / 100	452 ms	11100 KiB

tri

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> B;
typedef long long ll;
typedef pair<int,int> PII;
// head
  
const int N=100100;
const int S=1200;
int n,m;
  
struct pt {
  int x,y;
  pt(int _x=0,int _y=0) : x(_x),y(_y) {}
}p[N];

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

vector<pt> ch[N];
int orient(pt a,pt b,pt c) {
  ll v=(b.y-a.y)*1ll*(c.x-b.x)-(b.x-a.x)*1ll*(c.y-b.y);
  return v==0?0:(v<0?-1:1);
}

ll sgn(pt a, pt b, pt 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(pt{a.x - b.x, a.y - b.y}, pt{c.x - b.x, c.y - b.y});
  return (q / abs(q));
}

bool const operator<(const pt& a,const pt& b) {
  if (orient(pt(0,0),a,b)==0) {
    return (a.x==b.x?a.y<b.y:a.x<b.x);
  }
  return orient(pt(0,0),a,b)>0;
}

bool in_tri(pt a,pt b,pt c,pt p) {
  return orient(a,b,p)!=-1&&orient(b,c,p)!=-1&&orient(c,a,p)!=-1;
}

int main() {
  scanf("%d%d",&n,&m);
  rep(i,0,n) {
    scanf("%d%d",&p[i].x,&p[i].y);
  }
  sort(p,p+n);
  rep(i,0,n) {
    ch[i/S].pb(p[i]);
  }
  rep(i,0,n) {
    if (ch[i].empty()) continue;
    vector<pt> hull;
    sort(all(ch[i]),[&](pt a,pt b) { return a.x<b.x||(a.x==b.x&&a.y<b.y); });
    for (auto& p:ch[i]) {
      while (SZ(hull)>=2 && sgn(hull[SZ(hull)-2], p, hull[SZ(hull)-1])<=0) {
        hull.pop_back();
      }
      hull.pb(p);
    }
    ch[i]=hull;
  }
  while (m--) {
    pt a,b;
    scanf("%d%d%d%d",&a.x,&a.y,&b.x,&b.y);
    if (orient(b,pt(0,0),a)<=0) swap(a,b);
    int L,R;
    {
      L=n-1;
      int low=0,high=n-1;
      while (low<=high) {
        int mid=low+high>>1;
        if (orient(p[mid],pt(0,0),a)>=0) {
          L=mid;
          high=mid-1;
        } else {
          low=mid+1;
        }
      }
    }
    {
      R=0;
      int low=0,high=n-1;
      while (low<=high) {
        int mid=low+high>>1;
        if (orient(p[mid],pt(0,0),b)<=0) {
          R=mid;
          low=mid+1;
        } else {
          high=mid-1;
        }
      }
    }
    if (L>R) {
      printf("N\n");
      continue;
    }
    if (R-L<=S) {
      bool ok=false;
      rep(i,L,R+1) if (in_tri(a,b,pt(0,0),p[i])) ok=true;
      puts(ok?"Y":"N");
      continue;
    }
    bool ok=false;
    while (L%S!=0) {
      if (in_tri(a,b,pt(0,0),p[L])) ok=true;
      L++;
    }
    while (R>=L&&R%S!=S-1) {
      if (in_tri(a,b,pt(0,0),p[R])) ok=true;
      R--;
    }
    rep(i,L/S,R/S+1) {
      int sz=SZ(ch[i]);
      int low=0,high=sz-1;
      while (low<=high) {
        int mid=low+high>>1;
        if (in_tri(a,b,pt(0,0),ch[i][mid])) {
          ok=true;
          break;
        }
        if (mid+1==sz||(!in_tri(a,b,pt(0,0),ch[i][mid+1])&&orient(ch[i][mid],a,ch[i][mid+1])==1)) {
          high=mid-1;
        } else {
          low=mid+1;
        }
      }
      if (ok) break;
    }
    puts(ok?"Y":"N");
  }
}

Compilation message (stderr)

tri.cpp: In function 'int main()':
tri.cpp:86:20: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   86 |         int mid=low+high>>1;
      |                 ~~~^~~~~
tri.cpp:99:20: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   99 |         int mid=low+high>>1;
      |                 ~~~^~~~~
tri.cpp:131:20: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  131 |         int mid=low+high>>1;
      |                 ~~~^~~~~
tri.cpp:57:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |   scanf("%d%d",&n,&m);
      |   ~~~~~^~~~~~~~~~~~~~
tri.cpp:59:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   59 |     scanf("%d%d",&p[i].x,&p[i].y);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
tri.cpp:79:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   79 |     scanf("%d%d%d%d",&a.x,&a.y,&b.x,&b.y);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 100