{"id":328,"date":"2013-02-08T17:26:00","date_gmt":"2013-02-08T09:26:00","guid":{"rendered":"http:\/\/nike0good.jp1.rpvhost.net\/233"},"modified":"2013-02-08T17:26:00","modified_gmt":"2013-02-08T09:26:00","slug":"poj_1113wall-quickhull","status":"publish","type":"post","link":"https:\/\/nike0good.com\/?p=328","title":{"rendered":"POJ 1113(Wall-Quickhull)"},"content":{"rendered":"\n\n\n
\n
Language:\n\n\n\n
Time Limit:<\/strong> 1000MS<\/td>\n <\/td>\nMemory Limit:<\/strong> 10000K<\/td>\n<\/tr>\n
Total Submissions:<\/strong> 24604<\/td>\n <\/td>\nAccepted:<\/strong> 8183<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Description<\/p>\n

\nKing\u60f3\u5728\u81ea\u5df1\u7684n\u4e2a\u57ce\u5821\u5916\u5efaWall,\u4f7fWall\u4e0e\u4efb\u4e00\u57ce\u5821\u8ddd\u79bb\u81f3\u5c11\u4e3aL\u4e14\u80fd\u56f4\u4f4f\u5b83\u7684\u57ce\u5821. 
\n
\"\"<\/center>
\n
\n\u6c42Wall\u6700\u77ed\u957f\u5ea6. \n<\/div>\n

Input<\/p>\n

\n\u7b2c\u4e00\u884c\u4e3a N (3 <= N <= 1000) <\/span>\u548c L(1 <= L <= 1000).<\/div>\n
\n\u63a5\u4e0b\u6765 N \u884c,\u6bcf\u884c\u4e3a\u57ce\u5821\u5750\u6807Xi,Yi (-10000 <= Xi, Yi <= 10000).<\/div>\n

Output<\/p>\n

\n\u8f93\u51fa\u4e00\u884cWall\u6700\u77ed\u957f\u5ea6.<\/div>\n

Sample Input<\/p>\n

9 100\n200 400\n300 400\n300 300\n400 300\n400 400\n500 400\n500 200\n350 200\n200 200<\/pre>\n
Sample Output<\/p>\n
1628<\/pre>\n
Hint<\/p>\n
\n\u7ed3\u679c\u56db\u820d\u4e94\u5165\u5c31\u53ef\u4ee5\u4e86<\/div>\n
Source<\/p>\n
\nNortheastern Europe 2001<\/a><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
<\/p>\n
\u6613\u8bc1Wall\u6700\u77ed\u957f\u5ea6=\u5bf9\u57ce\u5821\u6c42\u51f8\u5305\u7684\u5468\u957f+2\u03c0L<\/span><\/p>\n
\u8fd9\u91cc\u4ecb\u7ecd\u4e00\u4e2a\u51f8\u5305\u6c42\u6cd5QuickHull<\/span><\/p>\n
\u5907\u6ce8Quickhull-<\/span><\/p>\n
s\u8868\u793a\u5411\u91cfCA<\/strong>\u4e0eCB<\/strong>\u7684\u53c9\u79ef(\u5728\u4e0a\u4e00\u6c42\u5f97\uff0c\u7528\u4e8e\u6c42\u8ddd\u79bb\uff09\uff0c\u521d\u59cb\u5316\u4e3a0<\/span><\/p>\n
\u7528[l,r]\u8868\u793a\u70b9\u96c6\u533a\u95f4\uff0c<\/span><\/p>\n
\u67092\u4e2a\u8981\u70b9<\/span><\/p>\n
1.A\uff0cB , C\u7684\u5173\u7cfb<\/span><\/p>\n
(1)<\/span><\/p>\n
\"\"<\/span><\/p>\n
(2)<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n
2.i,j\u7684\u8c03\u6362<\/span><\/p>\n
\u53ef\u4ece\u4e0b\u56fe\u770b\u51fa<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n
\"\"
\n<\/span><\/p>\n

\n<\/span><\/p>\n

\n<\/span><\/p>\n
\n<\/p>\n
\n<\/p>\n
<\/span><\/p>\n
#include<cstdio>\n#include<iostream>\n#include<cstdlib>\n#include<cstring>\n#include<cmath>\n#include<functional>\n#include<algorithm>\n#include<cctype>\nusing namespace std;\n#define MAXN (1000+10)\n#define MAXXi (10000+10)\n#define eps (1e-10)\nconst double pi=3.1415926;\nint sqr(int x) {return x*x;}\nstruct P\n{\n\tint x,y;\n\tP(){}\n\tP(int _x,int _y):x(_x),y(_y){}\n\tfriend istream& operator>>(istream &cin,P &a)\n\t{\n\t\tcin>>a.x>>a.y;\n\t\treturn cin;\n\t}\n\tfriend bool operator<(const P a,const P b){return (a.x==b.x)?a.y<b.y:a.x<b.x;}\n\tfriend bool operator>(const P a,const P b){return (a.x==b.x)?a.y>b.y:a.x>b.x;}\n}a[MAXN],st[MAXN];\ndouble dis(P A,P B)\n{\n\treturn sqrt((double)sqr(A.x-B.x)+sqr(A.y-B.y));\n}\nstruct V\n{\n\tint x,y;\n\tV(){}\n\tV(int _x,int _y):x(_x),y(_y){}\n\tV(P a,P b):x(b.x-a.x),y(b.y-a.y){}\n\tfriend int operator*(V a,V b)\n\t{\n\t\treturn a.x*b.y-a.y*b.x;\n\t}\n};\nint n,l,size=0;\ndouble s[MAXN]={0.0};\nvoid hull(int l,int r,P A,P B)\n{\n\tint p=l;\n\tfor (int k=l;k<=r;k++)\n\t\tif (s[p]<s[k]||s[p]==s[k]&&a[p]<a[k]) p=k;\n\tP C=a[p];\n\tint i=l-1,j=r+1;\n\tfor (int k=l;k<=r;k++)\n\t{\n\t\ts[++i]=V(a[k],A)*V(a[k],C);\n\t\tif (s[i]>0) \/*Right*\/ swap(a[i],a[k]); else i--;\n\t}\n\tfor (int k=r;k>=l;k--)\n\t{\n\t\ts[--j]=V(a[k],C)*V(a[k],B);\n\t\tif (s[j]>0) \/*Right*\/ swap(a[j],a[k]); else j++;\n\t}\n\tif (l<=i) hull(l,i,A,C);\n\tst[++size]=C;\n\tif (j<=r) hull(j,r,C,B);\n}\nint main()\n{\n\/\/\tfreopen("poj1113.in","r",stdin);\n\tcin>>n>>l;\n\tfor (int i=1;i<=n;i++)\n\t\tcin>>a[i];\n\tint pmin=1,pmax=1;\n\tfor (int i=2;i<=n;i++)\n\t{\n\t\tif (a[i]<a[pmin]) pmin=i;\n\t\tif (a[i]>a[pmax]) pmax=i;\n\t}\n\tswap(a[1],a[pmin]);swap(a[n],a[pmax]);\n\tst[++size]=a[1];\n\thull(2,n,a[1],a[1]);\n\/\/\tfor (int i=1;i<=size;i++) cout<<st[i].x<<' '<<st[i].y<<' '<<endl;\n\tdouble ans=0;\n\tfor (int i=1;i<=size;i++) ans+=dis(st[i],st[i+1<=size?i+1:1]);\n\tcout.setf(ios::fixed);\n\tcout.precision(0);\n\tcout<<ans+2*pi*l<<endl;\n\treturn 0;\n}<\/pre><\/p>\n","protected":false},"excerpt":{"rendered":"
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