poj1113Wall(凸包）

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顺便整理出来一份自己看着比较顺眼的模板

  1 #include <iostream>

  2 #include<cstdio>

  3 #include<cstring>

  4 #include<algorithm>

  5 #include<stdlib.h>

  6 #include<vector>

  7 #include<cmath>

  8 #include<queue>

  9 #include<set>

 10 using namespace std;

 11 #define N 1010

 12 #define LL long long

 13 #define INF 0xfffffff

 14 const double eps = 1e-8;

 15 const double pi = 3.141592653;

 16 const double inf = ~0u>>2;

 17 struct Point

 18 {

 19     double x,y;

 20     Point(double x=0,double y=0):x(x),y(y) {} //构造函数 方便代码编写

 21 }p[N],ch[N];

 22 typedef Point pointt;

 23 pointt operator + (Point a,Point b)

 24 {

 25     return Point(a.x+b.x,a.y+b.y);

 26 }

 27 pointt operator - (Point a,Point b)

 28 {

 29     return Point(a.x-b.x,a.y-b.y);

 30 }

 31 pointt operator * (Point a,double b)

 32 {

 33     return Point(a.x*b,a.y*b);

 34 }

 35 pointt operator / (Point a,double b)

 36 {

 37     return Point(a.x/b,a.y/b);

 38 }

 39 bool operator < (const Point &a,const Point &b)

 40 {

 41     return a.x<b.x||(a.x==b.x&&a.y<b.y);

 42 }

 43 int dcmp(double x)

 44 {

 45     if(fabs(x)<eps) return 0;

 46     else return x<0?-1:1;

 47 }

 48 bool operator == (const Point &a,const Point &b)

 49 {

 50     return dcmp(a.x-b.x)==0&&dcmp(a.y-b.y)==0;

 51 }

 52 //求点积以及利用点积求长度和夹角的函数

 53 double dot(Point a,Point b)

 54 {

 55     return a.x*b.x+a.y*b.y;

 56 }

 57 //叉积及叉积求面积

 58 double cross(Point a,Point b)

 59 {

 60     return a.x*b.y-a.y*b.x;

 61 }

 62 double  dis(Point a)

 63 {

 64     return sqrt(dot(a,a));

 65 }

 66 double mul(Point p0,Point p1,Point p2)

 67 {

 68     return cross(p1-p0,p2-p0);

 69 }

 70 bool cmp(Point a,Point b)

 71 {

 72     if(dcmp(mul(p[1],a,b))==0)

 73         return dis(a-p[1])<dis(b-p[1]);

 74     else

 75         return dcmp(mul(p[1],a,b))>0;

 76 }

 77 int Graham(int n)

 78 {

 79     int i,k = 1,top = 1;

 80     Point tmp;

 81     if(n<=3)

 82     {

 83         for(i = 1; i <= 3 ; i++)

 84             ch[i] = p[i];

 85         return n+1;

 86     }

 87     for(i = 1 ; i <= n; i++)

 88     {

 89         if(p[i].y<p[k].y||(p[i].y==p[k].y&&p[i].x<p[k].x))

 90             k = i;

 91     }

 92     if(k!=1)

 93     {

 94         tmp = p[1];  p[1] = p[k];  p[k] = tmp;

 95     }

 96     sort(p+2,p+n+1,cmp);

 97     ch[top++] = p[1];

 98     ch[top++] = p[2];

 99     ch[top++] = p[3];

100     for(i = 4; i <= n ;)

101     {

102         if(top<3||mul(ch[top-2],ch[top-1],p[i])>0)

103         {

104             ch[top++] = p[i++];

105         }

106         else  top--;

107     }

108     return top;

109 }

110 int main()

111 {

112     int i,n,r;

113     while(scanf("%d%d",&n,&r)!=EOF)

114     {

115         for(i = 1 ; i <= n ; i++)

116         {

117             scanf("%lf%lf",&p[i].x,&p[i].y);

118         }

119         int top = Graham(n);

120         ch[top] = p[1];

121         double ma;

122         ma = 2*pi*r;

123         for(i = 1 ; i < top ; i++)

124         {

125             ma += dis(ch[i]-ch[i+1]);

126         }

127         printf("%.0f\n",ma);

128     }

129     return 0;

130 }

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