POJ 2540 Hotter Colder--semi-flat cross

Test instructions: A (0,0) to (10,10) the rectangle, the target point is uncertain, starting from (0,0), if go to a new point is "hotter", then the meaning is close to the target point, if it is "Colder", then is far away, "same" is the same. To speculate on the area of the possible location of the target point.

Solution: Half-plane cross-water problem. From one point to another point far away, indicating the target point at two points between the perpendicular bisector of the source point closer to the side, that we can get a line each time to cut the plane, or cut to the left, or cut the right side, or all cut, and then a half-plane intersection can be obtained possible area.

Code:

#include <iostream>#include<cstdio>#include<cstring>#include<cstdlib>#include<cmath>#include<algorithm>#definePi ACOs (-1.0)#defineEPS 1e-8using namespacestd;structpoint{Doublex, y; Point (Doublex=0,Doubley=0): X (x), Y (y) {}voidInput () {scanf ("%LF%LF",&x,&y); }};typedef point Vector;structline{point P;    Vector v; Doubleang; Line () {} line (point P, Vector v):p (P), V (v) {ang=atan2 (v.y,v.x);} Point Point (DoubleT) {returnPoint (p.x + t*v.x, p.y + t*v.y); }    BOOL operator< (ConstLine &l)Const{returnAng <L.ang;}};intDCMP (Doublex) {if(x <-eps)return-1; if(X > EPS)return 1; return 0;} Template<classT> T Sqr (t x) {returnX *x;} Vectoroperator+ (vector A, vector B) {returnVector (a.x + b.x, A.Y +b.y); }vectoroperator-(vector A, vector B) {returnVector (a.x-b.x, A.Y-b.y); }vectoroperator* (Vector A,DoubleP) {returnVector (A.x*p, a.y*p); }vectoroperator/(Vector A,DoubleP) {returnVector (a.x/p, a.y/p); }BOOL operator< (Constpoint& A,Constpoint& b) {returna.x < b.x | | (a.x = = b.x && A.y <b.y); }BOOL operator>= (Constpoint& A,Constpoint& b) {returna.x >= b.x && a.y >=b.y;}BOOL operator<= (Constpoint& A,Constpoint& b) {returna.x <= b.x && a.y <=b.y;}BOOL operator== (Constpoint& A,Constpoint& b) {returnDCMP (a.x-b.x) = =0&& dcmp (a.y-b.y) = =0; }DoubleDot (vector A, vector B) {returna.x*b.x + a.y*b.y;}DoubleLength (Vector A) {returnsqrt (Dot (A, a));}DoubleAngle (vector A, vector B) {returnACOs (Dot (A, B)/Length (a)/Length (B)); }DoubleCross (vector A, vector B) {returna.x*b.y-a.y*b.x;} Vector vectorunit (vector x) {returnX/Length (x);} Vector Normal (vector x) {returnPoint (-X.Y, x.x)/Length (x);}DoubleAngle (Vector v) {returnatan2 (V.Y, v.x);} Point Getlineintersection (line A, line B) {Vector u= A.P-B.P; Doublet = Cross (B.V, u)/Cross (A.V, B.V); returnA.P + a.v*t;}DoubleDisP (Point a,point B) {returnLength (b-A);}DoubleCalcconvexarea (point* p,intN) {//Convex bag Area    DoubleArea =0.0;  for(intI=1; i<n-1; i++) Area+ = Cross (p[i]-p[0],p[i+1]-p[0]); returnFabs (area*0.5);}BOOLOnleft (line L, point P) {returnDCMP (Cross (L.V,P-L.P)) >0; }BOOLCmppolarline (line A,line b) {//linear Polar Angle sorting    returnAngle (A.V) <angle (B.V);}intHalfplaneintersection (line* L,intN, point* Poly) {//Half-plane intersection deposit PolySort (l,l+n,cmppolarline); intFirst,last; Point*p =NewPoint[n]; Line*q =NewLine[n]; Q[first=last=0] = l[0];  for(intI=1; i<n;i++) {         while(First < last &&!) Onleft (l[i],p[last-1])) last--;  while(First < last &&!) Onleft (L[i],p[first]) first++; q[++last] =L[i]; if(DCMP (Cross (Q[LAST].V, q[last-1].V)) = =0) { last--; if(Onleft (Q[last], L[I].P)) q[last] =L[i]; }        if(First < last) p[last-1] = Getlineintersection (q[last-1],q[last]); }     while(First < last &&!) Onleft (q[first],p[last-1])) last--; if(Last-first <=1)return 0;//point or line or unbounded plane, return 0P[last] =getlineintersection (Q[last],q[first]); intm =0;  for(inti=first;i<=last;i++) poly[m++] =P[i]; Delete p;    Delete q; returnm;} Line l[102],tl[103]; Point poly[104];intMain () {intI,j,tot =-1;    Point N,p; Charss[Ten]; P.x= P.Y =0.0; tl[++tot] = line (0,0), Vector (Ten,0)); tl[++tot] = line (Ten,0), Vector (0,Ten)); tl[++tot] = line (Ten,Ten), Vector (-Ten,0)); tl[++tot] = line (0,Ten), Vector (0,-Ten));  while(SCANF ("%lf%lf%s", &AMP;N.X,&AMP;N.Y,SS)! =EOF) {        if(ss[0] =='H') tl[++tot] = line ((n.x+p.x)/2.0, (N.Y+P.Y)/2.0), Vector (Normal (P-n))) ; Else if(ss[0] =='C') tl[++tot] = line ((n.x+p.x)/2.0, (N.Y+P.Y)/2.0), Vector (Normal (np)); Else{tl[++tot] = line ((n.x+p.x)/2.0, (N.Y+P.Y)/2.0), Vector (Normal (P-n))) ; tl[++tot] = line ((n.x+p.x)/2.0, (N.Y+P.Y)/2.0), Vector (Normal (np)); } P=N;  for(i=0; i<=tot;i++) L[i] =Tl[i]; intm = Halfplaneintersection (l,tot+1, poly); if(!m) puts ("0.00"); Elseprintf"%.2f\n", Calcconvexarea (poly,m)); }    return 0;}

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POJ 2540 Hotter Colder--semi-flat cross