Bzoj 1337 Minimum Circle cover stochastic increment method

Test Instructions:Link Method:Random Increment method parsing:Start by upsetting all the points. The first point is then enumerated, and if it is not within the current circle, it is set to the center. Then the second point is enumerated, and if it is not within the current circle, the circle is set to a circle with a diameter of its distance from the first point. Then enumerate the third point, and if it is not within the current circle, set the circle to the circumscribed circle of the three points that make up the triangle. And then the answer is finally. Don't ask me why this is right--! complexity expectation O (n), I am a letter. Code:

#include <cmath>#include <cstdio>#include <iomanip>#include <cstring>#include <iostream>#include <algorithm>#define N 100010using namespace STD;structpoint{Doublex, y;friendistream&operator>> (IStream &_,point &a) {scanf("%LF%LF", &AMP;A.X,&AMP;A.Y);return_; } point () {}, point (Double_x,Double_y): X (_x), Y (_y) {} pointoperator+ (ConstPoint &a) {returnPoint (X+A.X,Y+A.Y);} Pointoperator- (ConstPoint &a) {returnPoint (X-A.X,Y-A.Y);} Pointoperator* (DoubleRate) {returnPoint (X*rate,y*rate);}Double operator* (ConstPoint &a) {returnX*A.X+Y*A.Y;}Double operator^ (ConstPoint &a) {returnx*a.y-y*a.x;}} Pt[n];structline{Point P,v; Line () {A,point b):p (a), V (b) {}};structcircle{point P;DoubleR Circle () {} circle (Point _p,Double_r):p (_p), R (_r) {}}ans;DoubleDis (point &a,point &b) {return sqrt(A-B) * (a));BOOLIs_in_cir (Point &p,circle &c) {returnDis (P,C.P) &LT;=C.R;} Point Get_intersection (line &l1,line &l2) {point u=l1.p-l2.p;Doubletmp= (l2.v^u)/(L1.V^L2.V);returnl1.p+l1.v*tmp; }point rotate (Point a) {returnPoint (-a.y,a.x);}intNintMain () {Srand (19990329);scanf("%d", &n); for(intI=1; i<=n;i++)Cin>>pt[i]; Random_shuffle (pt+1, pt+n+1); for(intI=1; i<=n;i++) {if(!is_in_cir (Pt[i],ans)) {Ans.p=pt[i]; for(intj=1; j<i;j++) {if(!is_in_cir (Pt[j],ans)) {ans.p= (pt[i]+pt[j]) *0.5; Ans. R=dis (Pt[i],pt[j]) *0.5; for(intk=1; k<j;k++) {if(!is_in_cir (Pt[k],ans)) {line L1 (Pt[i]+pt[j]) *0.5, rotate (pt[i]-pt[j])); Line L2 ((Pt[i]+pt[k]) *0.5, rotate (pt[i]-pt[k]));                            Ans.p=get_intersection (L1,L2); Ans.                        R=dis (Ans.p,pt[i]); }                     }                }            }        }    }cout<<fixed<<setprecision (3) <<ans. R<<endl;}

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Bzoj 1337 Minimum Circle cover stochastic increment method