Lưu ý: Các code mẫu dưới đây chỉ mang tính tham khảo và có thể không AC được bài tập này

Code mẫu của RR

{$R+,Q+}
PROGRAM RECT1;
CONST
  fi='';
  fo='';
  maxn=10000;
TYPE
  rec=record x:real; d:integer; end;
  mang=array[1..maxn*2] of rec;
VAR
  n,na,nb:integer;
  xmax,ymax:longint;
  a,b:mang;
  kq:integer;
Procedure Add1(x,y:real);
Var
  gt:real;
Begin
  If y=0 then
    begin
      inc(nb); b[nb].x:=0; b[nb].d:=1;
      exit;
    end;
  If x=0 then
    begin
      inc(na); a[na].x:=0; a[na].d:=1;
      exit;
    end;
  gt:=ymax*x/y;
  if gt<>trunc(gt) then gt:=trunc(gt)+1;
  if gt>xmax then
    begin
      gt:=trunc(xmax*y/x);
      inc(nb);
      b[nb].x:=gt; b[nb].d:=1;
    end
  else
    begin
      inc(na);
      a[na].x:=gt; a[na].d:=1;
    end;
End;
Procedure Add2(x,y:real);
Var
  gt:real;
Begin
  If y=0 then
    begin
      inc(nb); b[nb].x:=0; b[nb].d:=-1;
      exit;
    end;
  If x=0 then
    begin
      inc(na); a[na].x:=0; a[na].d:=-1;
      exit;
    end;
  gt:=trunc(ymax*x/y);
  if gt>xmax then
    begin
      gt:=xmax*y/x+1;
      If gt<>trunc(gt) then gt:=trunc(gt)+1;
      inc(nb);
      b[nb].x:=gt; b[nb].d:=-1;
    end
  else
    begin
      inc(na);
      a[na].x:=gt; a[na].d:=-1;
    end;
End;
Procedure ReadInput;
Var
  f:text;
  i:integer;
  x1,y1,x2,y2:longint;
Begin
  Assign(f,fi); Reset(f);
  Readln(f,xmax,ymax,n);
  na:=0; nb:=0;
  For i:=1 to n do
    begin
      Readln(f,x1,y1,x2,y2);
      Add1(x1,y2);
      Add2(x2,y1);
    end;
  Close(f);
End;
Procedure WriteOutput;
Var
  f:text;
Begin
  Assign(f,fo); Rewrite(f);
  Writeln(f,kq);
  Close(f);
End;
Procedure QuickSort1(var a:mang;n:integer);
  Procedure Sort(l,r:integer);
  Var
    i,j:integer;
    tg,g:rec;
  Begin
    i:=l; j:=r; g:=a[(l+r) div 2];
    repeat
      while (a[i].x<g.x) or ((a[i].x=g.x) and (a[i].d>g.d)) do inc(i);
      while (a[j].x>g.x) or ((a[j].x=g.x) and (a[j].d<g.d)) do dec(j);
      if i<=j then
        begin
          tg:=a[i]; a[i]:=a[j]; a[j]:=tg;
          inc(i); dec(j);
        end;
    until i>j;
    if i<r then Sort(i,r);
    if l<j then Sort(l,j);
  End;
Begin
  Sort(1,n);
End;
Procedure QuickSort2(var a:mang;n:integer);
  Procedure Sort(l,r:integer);
  Var
    i,j:integer;
    tg,g:rec;
  Begin
    i:=l; j:=r; g:=a[(l+r) div 2];
    repeat
      while (a[i].x>g.x) or ((a[i].x=g.x) and (a[i].d>g.d)) do inc(i);
      while (a[j].x<g.x) or ((a[j].x=g.x) and (a[j].d<g.d)) do dec(j);
      if i<=j then
        begin
          tg:=a[i]; a[i]:=a[j]; a[j]:=tg;
          inc(i); dec(j);
        end;
    until i>j;
    if i<r then Sort(i,r);
    if l<j then Sort(l,j);
  End;
Begin
  Sort(1,n);
End;
Procedure Solve;
Var
  sl,i:integer;
Begin
  sl:=0;
  For i:=1 to na do
    begin
      sl:=sl+a[i].d;
      if sl>kq then kq:=sl;
    end;
  For i:=1 to nb do
    begin
      sl:=sl+b[i].d;
      if sl>kq then kq:=sl;
    end;
End;
BEGIN
  ReadInput;
  If na>1 then QuickSort1(a,na);
  If nb>1 then QuickSort2(b,nb);
  Solve;
  WriteOutput;
END.

Code mẫu của hieult

#include <set>
#include <map>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cctype>
#include <cstdio>
#include <string>
#include <vector>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iomanip>
#include <iostream>
#include <algorithm>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned int ui;
typedef unsigned long long ull;

#define Rep(i,n) for(typeof(n) i = 0; i < (n); ++i)
#define Repd(i,n) for(typeof(n) i = (n)-1; i >= 0; --i)
#define For(i,a,b) for(typeof(b) i = (a); i <= (b); ++i)
#define Ford(i,a,b) for(typeof(a) i = (a); i >= (b); --i)
#define Fit(i,v) for(typeof((v).begin()) i = (v).begin(); i != (v).end(); ++i)
#define Fitd(i,v) for(typeof((v).rbegin()) i = (v).rbegin(); i != (v).rend(); ++i)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(), (a).end()
#define ms(a,x) memset(a, x, sizeof(a))
#define nl puts("")
#define sp printf(" ")
#define ok puts("ok")
//#include <conio.h>

template<class F, class T> T convert(F a, int p = -1) { stringstream ss; if (p >= 0) ss << fixed << setprecision(p); ss << a; T r; ss >> r; return r; }
template<class T> void db(T a, int p = -1) { if (p >= 0) cout << fixed << setprecision(p); cout << a << " "; }
template<class T> T gcd(T a, T b) { T r; while (b != 0) { r = a % b; a = b; b = r; } return a; }
template<class T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
template<class T> T sqr(T x) { return x * x; }
template<class T> T cube(T x) { return x * x * x; }
template<class T> struct Triple { T x, y, z; Triple() {} Triple(T _x, T _y, T _z) : x(_x), y(_y), z(_z) {} };
template<class T> Triple<T> euclid(T a, T b) { if (b == 0) return Triple<T>(1, 0, a); Triple<T> r = euclid(b, a % b); return Triple<T>(r.y, r.x - a / b * r.y, r.z); }
template<class T> int getbit(T s, int i) { return (s >> i) & 1; }
template<class T> T onbit(T s, int i) { return s | (T(1) << i); }
template<class T> T offbit(T s, int i) { return s & (~(T(1) << i)); }
template<class T> int cntbit(T s) { return s == 0 ? 0 : cntbit(s >> 1) + (s & 1); }
const int bfsz = 1 << 16; char bf[bfsz + 5]; int rsz = 0;int ptr = 0;
char gc() { if (rsz <= 0) { ptr = 0; rsz = fread(bf, 1, bfsz, stdin); if (rsz <= 0) return EOF; } --rsz; return bf[ptr++]; }
void ga(char &c) { c = EOF; while (!isalpha(c)) c = gc(); }
int gs(char s[]) { int l = 0; char c = gc(); while (isspace(c)) c = gc(); while (c != EOF && !isspace(c)) { s[l++] = c; c = gc(); } s[l] = '\0'; return l; }
template<class T> bool gi(T &v) {
    v = 0; char c = gc(); while (c != EOF && c != '-' && !isdigit(c)) c = gc(); if (c == EOF) return false; bool neg = c == '-'; if (neg) c = gc();
    while (isdigit(c)) { v = v * 10 + c - '0'; c = gc(); } if (neg) v = -v; return true;
}

const double PI = 2 * acos(0);
const string months[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
const int days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
const int dr[] = {0, +1, 0, -1};
const int dc[] = {+1, 0, -1, 0};
const int inf = (int)1e9 + 5;
const ll linf = (ll)1e16 + 5;
const double eps = 1e-9;
const ll mod = 100000007;
typedef pair<int, int> II;

#define maxn 10005
#define maxe 100005

bool dcmp(double x, double y){
    return abs(x - y) < eps;
}

struct HCN{
    int x1, y1, x2, y2;
    double gl, gh;
    HCN(){};
    HCN(int _x1, int _y1, int _x2, int _y2){
        x1 = _x1; y1 = _y1; x2 = _x2; y2 = _y2;
        gl = atan2(y1, x2);
        gh = atan2(y2, x1);
    }
    bool operator < (const HCN &H)const{
        if(dcmp(gl, H.gl)) return gh < H.gh;
        return gl < H.gl;
    }
};

int n, x, y, f[maxn * 2] = {0};
HCN A[maxn];
vector<double> V;

int get(int u){
    int res = 0;
    for(int i = u; i < maxn * 2; i += i & -i) res += f[i];
    return res;
}

void update(int u){
    for(int i = u; i > 0; i -= i & -i) f[i]++;
}

double tinh(double goc){
    double u = atan2(y, x);
    int d;
    if(dcmp(u, goc)) return goc;
    if(goc < u){
        d = int(x * tan(goc) - eps) + 1;
        return atan2(d, x);
    }
    else{
        d = int(y * 1 / tan(goc));
        return atan2(y, d);
    }
}

int main() {
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    int x1, y1, x2, y2;
    scanf("%d %d %d", &x, &y, &n);
    Rep(i, n){
        scanf("%d %d %d %d", &x1, &y1, &x2, &y2);
        A[i] = HCN(x1, y1, x2, y2);
        //cout << A[i].gl << "  " << tinh(A[i].gl) << endl;
        V.pb(tinh(A[i].gl));
        V.pb(A[i].gh);
    }
    sort(A, A + n); sort(all(V));
    //Rep(i, n) cout << A[i].gl << "  " << A[i].gh << endl;
    //Rep(i, n)
    int res = 0, t;
    Rep(i, n){
        t = lower_bound(all(V), tinh(A[i].gl) + eps) - V.begin();
      //  cout << t << endl;
        res = max(res, get(t) + 1);
        t = lower_bound(all(V), A[i].gh + eps) - V.begin();
        update(t);
    }
    cout << res;

}

Code mẫu của ll931110

#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iostream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <vector>
typedef long long ll;
using namespace std;

int n;
double xmax,ymax;
vector< pair<double,int> > v;

int main()
{
//    freopen("rect.in","r",stdin);
//    freopen("rect.ou","w",stdout);
    scanf("%lf %lf %d", &xmax, &ymax, &n);
    for (int i = 0; i < n; i++)
    {
        double x1,y1,x2,y2;
        double dx,dy,tmp;
        scanf("%lf %lf %lf %lf", &x1, &y1, &x2, &y2);
        x1 = min(x1,xmax);  y1 = min(y1,ymax);  x2 = min(x2,xmax);  y2 = min(y2,ymax);

        //Insert bottom-right point
        tmp = ceil(xmax / x2 * y1);
        if (tmp <= ymax)
        {
           dx = xmax;  dy = tmp;
        }
        else
        {
           dy = ymax;  dx = trunc(ymax / y1 * x2);
        };
 //       cout << dx << ' ' << dy << endl;
        v.push_back(make_pair(atan2(dy,dx),0));

        //Insert top-left point
        tmp = ceil(ymax / y2 * x1);
        if (tmp <= xmax)
        {
           dy = ymax;  dx = tmp;
        }
        else
        {
            dx = xmax;  dy = trunc(xmax / x1 * y2);
        };
        v.push_back(make_pair(atan2(dy,dx),1));
    };

//    for (int i = 0; i < v.size(); i++) cout << v[i].first << ' ' << v[i].second << endl;

    sort(v.begin(),v.end()); 
//    for (int i = 0; i < v.size(); i++) cout << v[i].first << ' ' << v[i].second << endl;
    int ret = 0,cur = 0;
    for (int i = 0; i < v.size(); i++)
      if (v[i].second == 0)
      {
         cur++;  ret = max(ret,cur);
      }
      else cur--;
    printf("%d\n", ret);
};

Code mẫu của khuc_tuan

#include "stdio.h"
#include "vector"
#include "algorithm"

using namespace std;

#define maxn 100010
#define esp 1e-5

struct Rect {
    int x1, y1, x2, y2;
} a[maxn];    

int n, Xmax, Ymax, result;
vector<pair<int,int> > ds, dx;

void nhap() {
    scanf("%d%d%d",&Xmax, &Ymax, &n);
    for(int i=0;i<n;++i) {
        scanf("%d%d%d%d",&a[i].x1, &a[i].y1, &a[i].x2, &a[i].y2);
    }    
}    

void swap(int &x,int &y) {
    int t=x;x=y;y=t;
}    

void dao() {
    for(int i=0;i<n;++i) {
        swap(a[i].x1, a[i].y1);
        swap(a[i].x2, a[i].y2);
    }    
    swap(Xmax, Ymax);
}    

double timgiao(int x,int y) {
    if(x==0) return Ymax;
    if(x==Xmax) return y;
    double r = Xmax;
    r=r*y/x;
    return r;
}    

void init() {
    ds.clear();
    dx.clear();
    for(int i=0;i<n;++i) {
        double t1, t2;
        t1 = timgiao(a[i].x2,a[i].y1) ; 
        t2 = timgiao(a[i].x1,a[i].y2);
        if(t1>Ymax) continue;
        if(t2>Ymax) t2=Ymax;
        ds.push_back( make_pair( (int)(t1-esp+1), (int)(t2+esp)));
    }    
    for(int i=0;i<ds.size();++i) if(ds[i].first<=ds[i].second) {
        dx.push_back(make_pair(ds[i].first,1));
        dx.push_back(make_pair(ds[i].second,2));
    }    
    sort(dx.begin(),dx.end());
}    

void tinh() {
    init();
    int sl=0;
    for(int i=0;i<dx.size();++i) {
        if(dx[i].second==1) ++sl;
        else --sl;
        if(sl>result && (dx[i].first<=Ymax)) result=sl;
    }    
}    

void xuly() {
    result=0;
    tinh();
    dao();
    tinh();
    printf("%d\n", result);
}    

int main() {
    nhap();
    xuly();
//    system("pause");
    return 0;
}