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

Code mẫu của ladpro98

#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <climits>
#include <cstdlib>
#include <ctime>
#include <memory.h>
#include <cassert>
#include <climits>
#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define REP(i, a, b) for(int i = (a); i <=(b); i++)
#define FORD(i, a, b) for(int i = (a); i > (b); i--)
#define REPD(i, a, b) for(int i = (a); i >=(b); i--)
#define TR(it, a) for(typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define RESET(a, v) memset((a), (v), sizeof((a)))
#define SZ(a) (int((a).size()))
#define ALL(a) (a).begin(), (a).end()
#define PB push_back
#define MP make_pair
#define LL long long
#define LD long double
#define II pair<int, int>
#define X first
#define Y second
#define VI vector<int>
const int N = 2020;
const double eps = 1e-7;
using namespace std;

typedef pair<double, double> point;
bool eq(double a, double b) {return fabs(a - b) < eps;}
bool eq(point a, point b) {return eq(a.X, b.X) && eq(a.Y, b.Y);}

#define sqr(a) ((a) * (a))
double dist(point a, point b)
    {return sqrt(sqr(a.X - b.X) + sqr(a.Y - b.Y));}

struct line {
    point P, Q;
    double a, b, c;
    //aX + bY = c
    line() {}
    line(point _P, point _Q) {
        P = _P; Q = _Q;
        a = Q.Y - P.Y;
        b = P.X - Q.X;
        c = a * P.X + b * P.Y;
    }
};

point cutPoint(line d1, line d2) {
    double D  = d1.a * d2.b - d1.b * d2.a;
    double Dx = d1.c * d2.b - d1.b * d2.c;
    double Dy = d1.a * d2.c - d1.c * d2.a;
    return point(Dx / D, Dy / D);
}

bool isParallel(line d1, line d2)
    {return eq(d1.a * d2.b, d1.b * d2.a) && eq(d1.a * d2.c, d1.c * d2.a);}

bool inBetween(point a, point b, point c)
    {return eq(dist(a, b) + dist(b, c), dist(a, c));}
//end of helpers

int n, m;
line edge[N];
point in[N], out[N];

double len(point P, point Q) {
    //segment [PQ)
    line PQ (P, Q);
    FOR(i, 0, n) if (!isParallel(PQ, edge[i])) {
        point cut = cutPoint(PQ, edge[i]);
        if (inBetween(edge[i].P, cut, edge[i].Q)
         && inBetween(cut, Q, P)) return dist(Q, cut);
    }
}

int main() {
    ios :: sync_with_stdio(0); cin.tie(0);
    cin >> n;
    REP(i, 1, n) cin >> out[i].X >> out[i].Y;
    out[0] = out[n]; out[n + 1] = out[1];
    FOR(i, 0, n) edge[i] = line(out[i], out[i + 1]);
    cin >> m;
    REP(i, 1, m) cin >> in[i].X >> in[i].Y;
    in[0] = in[m]; in[m + 1] = in[1];
    double ans = 0;
    REP(i, 1, m)
        ans += dist(in[i - 1], in[i]) + min(len(in[i - 1], in[i]), len(in[i + 1], in[i]));
    cout << setprecision(4) << fixed << ans;
    return 0;
}

Code mẫu của RR

//Wishing myself a happy lunar new year with a lot of accept solutions
//Written by Nguyen Thanh Trung
const
  FINP='';
  FOUT='';
  maxn=2000;
type
  point=record x,y:real; end;
var
  m,n:integer;
  a,b:array[1..maxn] of point;
  g1,g2:array[1..maxn] of real;
procedure inp;
var
  f:text;
  i:integer;
begin
  assign(f,FINP); reset(f);
  readln(f,n);
  for i:=1 to n do
    with a[i] do
      readln(f,x,y);
  readln(f,m);
  for i:=1 to m do
    with b[i] do
      readln(f,x,y);
  close(f);
end;
function min(a,b:real):real;
begin
  if a<b then min:=a else min:=b;
end;
function kc(a,b:point):real;
begin
  kc:=sqrt(sqr(a.x-b.x)+sqr(a.y-b.y));
end;
function f(a,b,c:real;p:point):real;
begin
  f:=a*p.x+b*p.y+c;
end;
function cat(a,b,c,d:point;var p:point):boolean;
var
  a1,a2,b1,b2,c1,c2,Dx,Dy,Dd:real;
begin
  a1:=b.y-a.y;
  b1:=a.x-b.x;
  c1:=a.y*b.x-a.x*b.y;
  cat:=false;
  if f(a1,b1,c1,c)*f(a1,b1,c1,d)>0 then exit;
  a2:=d.y-c.y;
  b2:=c.x-d.x;
  c2:=c.y*d.x-c.x*d.y;
  Dx:=b1*c2-b2*c1;
  Dy:=c1*a2-c2*a1;
  Dd:=a1*b2-a2*b1;
  p.x:=Dx/Dd;
  p.y:=Dy/Dd;
  if kc(a,p)<kc(b,p) then exit;
  cat:=true;
end;
procedure solve;
var
  i,j,k,ii,jj:integer;
  p:point;
  ok:boolean;
begin
  j:=1;
  for i:=1 to m do
    begin
      ok:=false;
      while not ok do
        begin
          if j=n+1 then j:=1;
          jj:=j+1; if jj=n+1 then jj:=1;
          ii:=i+1; if ii=m+1 then ii:=1;
          if cat(b[i],b[ii],a[j],a[jj],p) then
            begin
              ok:=true;
              g1[i]:=kc(p,b[ii]);
            end
          else inc(j);
        end;
    end;
  j:=0;
  for i:=2 to m+1 do
    begin
      ok:=false;
      k:=i; if k=m+1 then k:=1;
      while not ok do
        begin
          inc(j); if j=n+1 then j:=1;
          jj:=j+1; if jj=n+1 then jj:=1;
          ii:=k+1; if ii=m+1 then ii:=1;
          if cat(b[ii],b[k],a[j],a[jj],p) then
            begin
              ok:=true;
              g2[i-1]:=kc(p,b[k]);
            end;
        end;
    end;
end;
procedure ans;
var
  f:text;
  kq:real;
  i,ii:integer;
begin
  assign(f,FOUT); rewrite(f);
  kq:=0;
  for i:=1 to m do
    begin
      ii:=i+1; if ii=m+1 then ii:=1;
      kq:=kq+kc(b[i],b[ii]);
    end;
  for i:=1 to m do
    kq:=kq+min(g1[i],g2[i]);
  writeln(f,kq:0:4);
  close(f);
end;
begin
  inp;
  solve;
  ans;
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 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, 0, -1, +1};
const int dc[] = {-1, +1, 0, 0};
const int inf = (int)1e9 + 5;
const ll linf = (ll)1e16 + 5;
const double eps = ld(1e-9);
const ll mod = 100000007;
typedef pair<int, int> II;


#define maxn 2005
#define maxv 1005

struct Point{
    ld x, y;
    Point() {};
    Point(ld _x, ld _y){
        x = _x; y = _y;
    }
};

Point O;

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

bool dcmpPoint(Point A, Point B){
    return dcmp(A.x, B.x) && dcmp(A.y, B.y);
}

int ccw(Point A, Point B, Point C){
    ld dx1 = B.x - A.x, dy1 = B.y - A.y;
    ld dx2 = C.x - A.x, dy2 = C.y - A.y;
    ld ret = dx1 * dy2 - dy1 * dx2;
    if(dcmp(ret, 0)) return 0;
    return ret < 0 ? -1 : 1;
}

ld sqrDist(Point P1, Point P2){
    return sqr(P1.x - P2.x) + sqr(P1.y - P2.y);
}

bool nearer(Point P1, Point P2){
    return sqrDist(O, P1) < sqrDist(O, P2);
}

bool cmp(Point P1, Point P2){
    int c = ccw(O, P1, P2);
    if(c != 0) return c > 0;
    return nearer(P1, P2);
}

void graham(Point a[], int &n){
    if(n < 3) return;
    int imin = 0;
    For(i, 1, n - 1) if((a[i].y < a[imin].y) || (a[i].y == a[imin].y && a[i].x < a[imin].x)) imin = i;
    O = a[imin];
    swap(a[0], a[imin]);
    sort(a + 1, a + n, cmp);
    int inow = 1;
    For(i, 2, n - 1){
        while(inow > 0 && ccw(a[i], a[inow], a[inow - 1]) >= 0) --inow;
        ++inow;
        swap(a[inow], a[i]);
    }
    n = inow + 1;
}

void getLine(Point P0, Point P1, ld &a, ld &b, ld &c){
    a = P1.y - P0.y; b = P0.x - P1.x; c = -(a * P0.x + b * P0.y);
}

bool getIntersect(Point P0, Point P1, Point P2, Point P3, Point &P4){
    ld a0, b0, c0, a1, b1, c1;
    getLine(P0, P1, a0, b0, c0);
    getLine(P2, P3, a1, b1, c1);
    ld d = a0 * b1 - a1 * b0;
    ld dx = b0 * c1 - b1 * c0;
    ld dy = c0 * a1 - c1 * a0;

    if(dcmp(d, 0)) return 0;

    P4 = Point(dx / d, dy / d);
    return 1;
}

ld area(Point a[], int n){
    ld res = 0;
    Rep(i, n) res += (a[i].x * a[(i + 1) % n].y - a[i].y * a[(i + 1) % n].x);
    return abs(res) / 2;
}

int n, m;
Point A[maxn], B[maxn];
vector<double> V[maxn];

double cal(){
    double res = 0;
    Rep(i, m) res += sqrt(sqrDist(B[i], B[(i + 1) % m]));
    return res;
}

bool namgiua(Point P0, Point P1, Point P2){
    if(dcmpPoint(P0, P2)) return true;
    if(dcmpPoint(P0, P1)) return false;
    if(dcmp(P1.x, P2.x)) return (P0.y - P1.y) * (P0.y - P2.y) < 0;
    return (P0.x - P1.x) * (P0.x - P2.x) < 0;
}

int main(){
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);

    scanf("%d", &n);
    Rep(i, n) scanf("%lf %lf", &A[i].x, &A[i].y);
    scanf("%d", &m);
   // cout << m << endl;
    Rep(i, m) scanf("%lf %lf", &B[i].x, &B[i].y);
    graham(A, n); graham(B, m);
    double res = cal();
    Point P;
    Rep(i, m){
        int j = (i + 1) % m, u, v;
        for(u = 0; u < n; u++){
            v = (u + 1) % n;
            if(getIntersect(B[i], B[j], A[u], A[v], P) && namgiua(P, A[u], A[v])){
                if(sqrDist(B[i], P) < sqrDist(B[j], P)) V[i].pb(sqrt(sqrDist(B[i], P)));
                else V[j].pb(sqrt(sqrDist(B[j], P)));
            }
        }
    }

    Rep(i, m){ sort(all(V[i])); res += V[i][0]; }
    printf("%.4lf\n", res);

    return 0;
}