Andrew似乎是Graham的上位替代?
反正15行的代码长度还是很有保存价值的
//#include<bits/stdc++.h> //#pragma comment(linker, "/STACK:1024000000,1024000000") #include<stdio.h> #include<algorithm> #include<queue> #include<string.h> #include<iostream> #include<math.h> #include<set> #include<map> #include<vector> #include<iomanip> using namespace std; const double pi=acos(-1.0); #define ll long long #define pb push_back #define sqr(a) ((a)*(a)) #define dis(a,b) sqrt(sqr(a.x-b.x)+sqr(a.y-b.y)) const int maxn=1e3+56; const int inf=0x3f3f3f3f; int n; struct Point{ double x,y; Point(){} Point(double x,double y):x(x),y(y){} Point operator+(const Point& rhs)const{return Point(x+rhs.x,y+rhs.y);} Point operator-(const Point& rhs)const{return Point(x-rhs.x,y-rhs.y);} Point operator*(const double d)const{return Point(d*x,d*y);} double cross(const Point &rhs)const{ return (x*rhs.y-y*rhs.x); } }point[maxn],vertex[maxn]; bool cmp_x(const Point a,const Point b){ if(a.x==b.x)return a.y<b.y; else return a.x<b.x; } int Andrew(){ //返回凸包顶点数 sort(point,point+n,cmp_x); int k=0; for(int i=0;i<n;i++){ while(k>1 && (vertex[k-1]-vertex[k-2]).cross(point[i]-vertex[k-1])<=0)k--; vertex[k++]=point[i]; } int m=k; for(int i=n-2;i>=0;i--){ while(k>m && (vertex[k-1]-vertex[k-2]).cross(point[i]-vertex[k-1])<=0)k--; vertex[k++]=point[i]; } if(k>1)k--; //k=1凸包退化 return k; } void solve(){ //求凸包面积,计算方式是凸包底边三角形的面积并 int tot=Andrew(); if(tot<=2){printf("0 ");return;} double area=0; for(int i=2;i<tot;i++){ double a=dis(vertex[i-1],vertex[0]); double b=dis(vertex[i],vertex[0]); double c=dis(vertex[i],vertex[i-1]); double p=(a+b+c)/2; area+=sqrt(p*(p-a)*(p-b)*(p-c)); } printf("%d ",(int)(area/50.0)); //每头牛50平米面积 } int main(){ while(~scanf("%d",&n)){ for(int i=0;i<n;i++){ scanf("%lf%lf",&point[i].x,&point[i].y); } solve(); } }