HDU2899 （三分）

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 1 #include<stdio.h>
 2 #include<math.h>
 3 
 4 double func( double x,double y ){
 5     double ans;
 6     ans=6*pow( x,7.0 )+8*pow( x,6.0 )+7*pow( x,3.0 )+5*pow( x,2.0 )-y*x;
 7     return ans;
 8 }
 9 
10 int main(){
11     int T;
12     scanf("%d",&T);
13     while( T-- ){
14         double y;
15         scanf("%lf",&y);
16         double left,right,mid,mmid;
17         left=0,right=100;
18         double delta=1e-8;
19         while( left<right-delta ){
20             mid=(left+right)/2.0;
21             mmid=( mid+right )/2.0;
22             if( func( mid,y )<func( mmid,y ) ) right=mmid;
23             else left=mid;
24         }
25         printf("%.4lf\n",func( mid,y ));
26     }
27     return 0;
28 }

满足函数的凹凸性即可用三分。

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