Hdu 5563 Clarke and five-pointed Star (enumeration)

Test instructions: Give the coordinates of 5 points and ask whether the 5 points are exactly the vertices of a pentagram.

Ideas:

The DFS enumerates the order of 5 points.

Judge 5 adjacent edges equal and 5 diagonal lines equal. If all are satisfied then yes, otherwise not.

Attached: Why should we judge 5 diagonal lines equally?

, a square above a positive triangle, also satisfies 5 adjacent edges equal, but does not satisfy 5 diagonal lines equal.

Code:

1#include <cstdio>2#include <cstring>3#include <iostream>4#include <algorithm>5#include <cstdlib>6#include <cmath>7#include <vector>8#include <queue>9#include <map>Ten#include <Set> One #defineEPS 10e-6 A  - using namespacestd; -  the Doublex[8],y[8]; - BOOLvis[8]; - intorder[6]; - Doubledis[ A]; +  - DoubleCalintIintj) + { A     return(X[i]-x[j]) * (X[i]-x[j]) + (Y[i]-y[j]) * (y[i]-y[j]); at } -  - BOOLisOK () - { -      for(intI=0;i<4; i++) -Dis[i] = cal (order[i+1],order[i+2]); indis[4] = cal (order[5],order[1]); -     intFlag1 =1; to      for(intI=0;i<4; i++) +     { -         if(Fabs (dis[i]-dis[4]) >EPS) the         { *Flag1 =0; $              Break;Panax Notoginseng         } -     } the  +dis[5] = cal (order[1],order[3]); Adis[6] = cal (order[1],order[4]); thedis[7] = cal (order[2],order[4]); +dis[8] = cal (order[2],order[5]); -dis[9] = cal (order[3],order[5]); $     intFlag2 =1; $      for(intI=5;i<9; i++) -     { -         if(Fabs (dis[i]-dis[9]) >EPS) the         { -Flag2 =0;Wuyi              Break; the         } -     } Wu     returnFlag1 &&Flag2; - } About  $ BOOLDfsintPOS) - { -     if(pos = =6) -     { A         if(isOK ()) +             return true; the     } -      for(intI=0;i<5; i++) $     { the         if(!Vis[i]) the         { theOrder[pos] =i; theVis[i] =true; -             if(Dfs (pos+1))return true; inVis[i] =false; the         } the     } About     return false; the } the  the intMain () + { -     intT; thescanf"%d",&T);Bayi      while(t--) the     { thememset (Vis,0,sizeof(Vis)); -          for(intI=0;i<5; i++) -scanf"%LF%LF",&x[i],&y[i]); the         if(Dfs (1)) puts ("Yes"); the         ElsePuts"No"); the     } the     return 0; -}

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Hdu 5563 Clarke and five-pointed Star (enumeration)