Ural 1246. Tethered Dog

1246. Tethered DogTime limit:1.0 Second
Memory limit:64 MBA Dog is tethered to a pole with a rope. The pole is located inside a fenced polygon, not necessarily convex, with nonzero area. The fence has no self-crosses. The Olympian runs along the fence bypassing the vertices of the polygon in a certain order which are not broken during the Jog. A Dog pursues him inside the fenced territory and barks. Your program was to determine how (clockwise or counter-clockwise) the rope would wind after several rounds of the Olympian ' S jog. Inputthe first input line contains a number NThat's the number of the polygon vertices. It ' s known that 3≤ N≤200000. The next NLines consist of the vertices plane coordinates, given in an order of Olympian ' s dog. The coordinates is a pair of integers separated with a space. The absolute value of each coordinate doesn ' t exceed 50000.OutputYou was to output "CW" If the rope is winded in a clockw Ise Order and "CCW" otherwise. Sample

input	Output
40 00 11) 11 0	cw

problem Author:Evgeny Kobzev
problem Source:Ural State University Personal Programming Contest, March 1, 2003 Tags:Geometry()difficulty:364 Test Instructions: Ask if the given order of a polygon is clockwise. Analysis: Cross product judgment direction. Use the leftmost or most optimal point as the datum point.

1#include <cstdio>2#include <cstring>3#include <cstdlib>4#include <cmath>5#include <deque>6#include <vector>7#include <queue>8#include <iostream>9#include <algorithm>Ten#include <map> One#include <Set> A#include <ctime> -#include <iomanip> - using namespacestd; thetypedefLong LongLL; -typedefDoubleDB; - #defineFor (I, S, T) for (int i = (s); I <= (t); i++) - #defineFord (I, S, T) for (int i = (s); I >= (t); i--) + #defineRep (i, T) for (int i = (0); i < (t); i++) - #defineREPN (i, T) for (int i = (t)-1); I >= (0); i--) + #defineRep (i, X, T) for (int i = (x); i < (t); i++) A #defineMIT (2147483647) at #defineINF (1000000001) - #defineMLL (1000000000000000001LL) - #defineSZ (x) ((int) (x). Size ()) - #defineCLR (x, y) memset (x, y, sizeof (x)) - #definePUF Push_front - #definePub push_back in #definePOF Pop_front - #definePOB pop_back to #defineFT first + #defineSD Second - #defineMk Make_pair theInlinevoidSetio (stringName) * { $     stringInput = name+". in",Panax NotoginsengOutput = name+". out"; -Freopen (Input.c_str (),"R", stdin), theFreopen (Output.c_str (),"W", stdout); + } A  theInlineintGetint () + { -     intRet =0; $     CharCh =' '; $     BOOLFlag =0; -      while(! (Ch >='0'&& Ch <='9')) -     { the         if(Ch = ='-') Flag ^=1; -Ch =GetChar ();Wuyi     } the      while(Ch >='0'&& Ch <='9') -     { WuRET = RET *Ten+ Ch-'0'; -Ch =GetChar (); About     } $     returnFlag? -Ret:ret; - } -  - Const intN =200010; A struct Point + { the DB x, y; -InlinevoidRead () $     { thescanf"%LF%LF", &x, &y); the     } the } Arr[n]; the intN; -  inInlinevoidInput () the { thescanf"%d", &n); Aboutfor (I,1, N) Arr[i]. Read (); the } the  theInline DB Det (ConstPoint &a,ConstPoint &o,ConstPoint &B) + { -DB X1 = a.x-o.x, X2 = b.x-o.x; theDB Y1 = a.y-o.y, Y2 = b.y-o.y;Bayi     returnX1 * Y2-X2 *Y1; the } the  -InlinevoidSolve () - { the     intp =1; thefor (I,2, N) the         if(arr[i].x > arr[p].x) p =i; thearr[0] = Arr[n], arr[n +1] = arr[1]; -     if(Det (Arr[p-1], Arr[p], arr[p +1]) >=0.0) puts ("CW"); the     ElsePuts"CCW"); the } the 94 intMain () the { the #ifndef Online_judge theSetio ("E");98     #endif  About Input (); - Solve ();101     return 0;102}

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Ural 1246. Tethered Dog