UVA 10256 the Great Divide (convex hull, polygon position Relationship)

Title Link: http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=34148

Ideas

Convex bag

Find out the red and blue dot convex hull, the remaining problem is to determine whether two convex bag is absent.

You need to determine two points:

1) intersection of segments on convex package

2) The points on the convex hull are included in the other convex package.

Code

1#include <cmath>2#include <vector>3#include <cstdio>4#include <algorithm>5 using namespacestd;6 7 Const DoubleEPS = 1e-Ten;8 intDCMP (Doublex) {9     if(Fabs (x) <eps)return 0;Else returnx<0? -1:1;Ten } One  A structPt { -     Doublex, y; -Pt (Doublex=0,Doubley=0): X (x), Y (y) {}; the }; - typedef Pt VEC; -Vecoperator-(Pt a,pt B) {returnVEC (a.x-b.x,a.y-b.y); } - BOOL operator==(Pt a,pt B) { +     returnDCMP (a.x-b.x) = =0&& dcmp (a.y-b.y) = =0; - } + BOOL operator< (Constpt& A,Constpt&b) { A     returna.x<b.x | | (a.x==b.x && a.y<b.y); at } - DoubleDot (VEC A,vec B) {returna.x*b.x+a.y*b.y;} - DoubleCross (Pt a,pt B) {returna.x*b.y-a.y*b.x;} -  - BOOLsegintersection (Pt a1,pt a2,pt b1,pt b2) { -     DoubleC1 = Cross (A2-A1,B1-A1), C2 = Cross (a2-a1,b2-A1), inC3 = Cross (B2-B1,A1-B1), C4=cross (b2-b1,a2-B1); -   returnDCMP (C1) *dcmp (C2) <0&& dcmp (C3) *dcmp (C4) <0; to } + BOOLonseg (Pt p,pt a1,pt A2) { -     returnDCMP (Cross (p-a1,p-a2)) = =0&& dcmp (Dot (P-A1,P-A2)) <0; the } *  $ Panax Notoginseng intN; -Vector<pt> Convexhull (vector<pt>p) { the sort (P.begin (), P.end ()); + p.erase (Unique (P.begin (), P.end ()), P.end ()); A     intn=p.size (); the     intm=0; +Vector<pt> CH (n+1); -      for(intI=0; i<n;i++) { $          while(m>1&& Cross (ch[m-1]-ch[m-2],p[i]-ch[m-2]) <=0) m--; $ch[m++]=P[i]; -     } -     intk=m; the      for(inti=n-2; i>=0; i--) { -          while(M>k && Cross (ch[m-1]-ch[m-2],p[i]-ch[m-2]) <=0) m--;Wuyich[m++]=P[i]; the     } -     if(n>1) m--; Wu ch.resize (m); -     returnch; About } $  - intIspointinpolygon (Pt p,vector<pt>&Poly) { -     intwn=0; -     intn=poly.size (); A      for(intI=0; i<n;i++) { +pt& p1=Poly[i]; thept& p2=poly[(i+1)%n]; -         if(p1==p | | p2==p | | Onseg (P,P1,P2))return-1; $         intK=DCMP (Cross (p2-p1,p-p1)); the         intD1=DCMP (p1.y-p.y); the         intD2=DCMP (p2.y-p.y); the         if(k>0&& d1<=0&& d2>0) wn++; the         if(k<0&& d2<=0&& d1>0) wn--; -     } in     if(wn!=0)return 1; the     return 0; the } About BOOLConvexpolygondisjoint (vector<pt> ch1,vector<pt>CH2) { the     intC1=ch1.size (), c2=ch2.size (); the      for(intI=0; i<c1;i++) the         if(Ispointinpolygon (CH1[I],CH2)! =0)return false; +      for(intI=0; i<c2;i++) -         if(Ispointinpolygon (ch2[i],ch1)! =0)return false; the      for(intI=0; i<c1;i++)Bayi          for(intj=0; j<c2;j++) the             if(Segintersection (ch1[i],ch1[(i+1)%c1],ch2[j],ch2[(j+1)%C2]))return false; the     return true; - } -  the intMain () { the     intn,m; the      while(SCANF ("%d%d", &n,&m) = =2&& N &&m) { theVector<pt>p1,p2; -         Doublex, y; the          for(intI=0; i<n;i++) { thescanf"%LF%LF",&x,&y); the P1.push_back (Pt (x, y));94         } the          for(intI=0; i<m;i++) { thescanf"%LF%LF",&x,&y); the P2.push_back (Pt (x, y));98         } About         if(Convexpolygondisjoint (Convexhull (P1), Convexhull (P2))) -Puts"Yes");ElsePuts"No");101     }102     return 0;103}

UVA 10256 the Great Divide (convex hull, polygon position Relationship)