C++-hihoCoder-1142-三分求极值[三分]

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef double db;
 4 const db eps=1e-9;
 5 db a,b,c,x,y;
 6 db dis2(db X){
 7     db Y=a*X*X+b*X+c;
 8     return (X-x)*(X-x)+(Y-y)*(Y-y);
 9 }
10 db third(){
11     db l=-200,r=200,ans1,ans2;
12     while(r-l>eps){
13         db ll=(2*l+r)/3,rr=(l+2*r)/3;
14         ans1=dis2(ll);ans2=dis2(rr);
15         ans1<ans2?r=rr:l=ll;
16     }
17     return sqrt(ans1);
18 }
19 int main(){
20     scanf("%lf%lf%lf%lf%lf",&a,&b,&c,&x,&y);
21     printf("%.3f
",third());
22     return 0;
23 }

~~Jason_liu O(∩_∩)O