POJ 1113 Wall (convex bag)

Links: Poj 1113

Test Instructions : n vertices of a given polygon castle. Build a fence around the castle, surround all points,

and the distance between the wall and all points is at least L. ask for the smallest length of the wall.

Ideas : Minimum length = The total edge length of the convex hull consisting of the castle vertices + the circumference of the circle with a radius of L

First, the convex hull is obtained by the Graham algorithm. Then enumerate its vertices to find the length of the edge between 22. Remember to add the edge length of the first vertex and the last vertex

The final output rounded integer result, can be saved with double, and finally output with%.0LF

#include <cstdio> #include <cstring> #include <algorithm> #include <cmath>using namespace std; struct stu{int x, y;} P[1010],s[1010];int m,top;int Chaji (struct stu p1,struct stu p2,struct Stu P3) {return (p1.x-p2.x) * (P3.Y-P2.Y)-(P3.X-P2 . x) * (P1.Y-P2.Y);} Double dis (struct stu p1,struct stu p2) {return sqrt ((p1.x-p2.x) * (p1.x-p2.x) *1.0+ (P1.Y-P2.Y) * (P1.Y-P2.Y));}    int cmp (struct stu p1,struct stu p2) {int k;    K=chaji (P1,P[0],P2); if (k>0| |        (K==0&&dis (p1,p[0]) <dis (p2,p[0])))    return 1; return 0;}    void Graham () {struct Stu T;    int k=0,i; for (i=1;i<m;i++) if (p[i].y<p[k].y| |            (p[i].y==p[k].y&&p[i].x<p[k].x))    K=i;    T=P[K];    P[K]=P[0];    p[0]=t;    Sort (p+1,p+m,cmp);    S[0]=P[0];    S[1]=P[1];    Top=1;        for (i=2;i<m;i++) {while (Top>=1&&chaji (S[top-1],s[top],p[i]) >=0) top--;        top++;    S[top]=p[i];    }}int Main () {int n,i;    Double sum; while (scanf("%d%d", &m,&n)!=eof) {for (i=0;i<m;i++) scanf ("%d%d", &p[i].x,&p[i].y);        Graham ();        Sum=dis (S[0],s[top]) +2*3.1415926*n;        for (i=1;i<=top;i++) Sum+=dis (S[i-1],s[i]);    printf ("%.0lf\n", sum); } return 0;}

POJ 1113 Wall (convex bag)