Codeforces 8D Two Friends 三分+二分+計算幾何

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題目連結：點擊開啟連結

題意：點擊開啟連結

三分house到shop的距離，二分這條斜邊到cinema的距離

#include<stdio.h>#include<string.h>#include<iostream>#include<algorithm>#include<math.h>#include<set>#include<queue>#include<vector>#include<map>using namespace std;#define ll int#define N 90#define Pi 3.1415926535898#define eps 1e-10double t1, t2;struct node{double x,y;}c,h,s;double dist(double x1,double y1,double x2,double y2){return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));}double dist(node a,node b){return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}double work(double du){node x = {s.x*(1-du) + h.x*du, s.y*(1-du)+h.y*du};double ac = dist(x,c), as = dist(x,s), ah = dist(x,h);if(ac+ah<=t2&&ac+as<=t1)return min(t2-ah,t1-as);double l = 0, r = 1.0;for(int i = 1; i <= 300 ; i++){double mid = (l+r)/2;node b = {c.x*(1-mid)+x.x*mid,c.y*(1-mid)+x.y*mid};double bc = dist(b,c), bs = dist(b, s), bh = dist(b, h);if(bc+bh<=t2 && bc+bs<=t1) l = mid;else r = mid;}node b = {c.x*(1-l)+x.x*l, c.y*(1-l)+x.y*l};return dist(b,c);}int main(){  ll i, j, u, v;while(cin>>t1>>t2){cin>>c.x>>c.y;cin>>h.x>>h.y;cin>>s.x>>s.y;double a = dist(c,s), b = dist(c,h), c = dist(h,s);if(b+t2>=a+c){printf("%.8lf\n",min(a+t1+c,b+t2));continue;}t1+=a+eps; t2+=b+eps;double l = 0, r = 1.0, ans = 0;for(i = 1; i <= 300; i++){double mid1 = (l+r)/2.0, mid2 = (mid1+r)/2.0;double ans1 = work(mid1), ans2 = work(mid2);if(ans1<ans2) l = mid1;else r = mid2;ans = max(ans, max(ans1,ans2));}printf("%.8lf\n",ans);}return 0;}