PTA sets a basic programming topics

K 7-13 day candle (15 points)

https://pintia.cn/problem-sets/14/problems/793

AC Code:

 1 #include <cstdio>
 2 #include <cmath>
 3 #include <algorithm>
 4 using namespace std;
 5 int main()
 6 {
 7     double open,high,low,close;
 8     scanf("%lf %lf %lf %lf",&open,&high,&low,&close);
 9     if(open>close) printf("BW-Solid");
10     else if(open==close) printf("R-Cross");
11     else printf("R-Hollow");
12     if((high>open&&high>close)&&(low<open&&low<close)) printf(" with Lower Shadow and Upper Shadow\n");
13     else if(high>open&&high>close) printf(" with Upper Shadow\n");
14     else if(low<close&&low<open) printf(" with Lower Shadow\n");
15     return 0;
16  } 

 7-18 dichotomy single polynomial (20 minutes)

 https://pintia.cn/problem-sets/14/problems/798

AC Code:

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <cmath>
 4 #include <algorithm>
 5 using namespace std;
 6 double fal(double a3,double a2,double a1,double a0,double x)
 7 {
 8     double value=a3*x*x*x+a2*x*x+a1*x+a0;
 9     return value; 
10 }
11 int main()
12 {
13     double a3,a2,a1,a0,x;
14     double low,high,mid;
15     double threshold=0.001;
16     double value1,value2,value3;
17     scanf("%lf %lf %lf %lf",&a3,&a2,&a1,&a0);
18     scanf("%lf %lf",&low,&high);
19     while(high-low>=threshold)
20     {
21         value1=fal(a3,a2,a1,a0,low);
22         value2=fal(a3,a2,a1,a0,high);
23         if(value1*value2==0){
24             if(value1==0){
25                 printf("%.2f\n",low);
26                 break;
27             }
28             else if(value2==0)
29             {
30                 printf("%.2f\n",high);
31                 break;
32             }
33         }
34         else{
35             if(value1*value2<0)
36             {
37                 mid=(high+low)/2;
38                 value3=fal(a3,a2,a1,a0,mid);
39                 if(value3==0)
40                 {
41                     printf("%.2f\n",mid);
42                     break;
43                 }
44                 else if(value1*value3<0) high=mid;
45                 else if(value2*value3<0) low=mid; 
46             }
47             else if(value1*value2>0) break;
48         }
49     }
50     if(high-low<threshold){
51        // if(fal(a3,a2,a1,a0,low)==0) printf("%.2lf\n",low);
52         //else if(fal(a3,a2,a1,a0,high)==0) printf("%.2lf\n",high);
53         printf("%.2f\n",(low+high)/2);
54     }
55     return 0;
56 }

My day, my card this problem for a long time, the first few submitted are partially true, does not consider the case when the endpoint function value is 0, then added a conditional judgment in the while loop, and then submit the output did not even answer, then I think it is not a double input and output formatting issues, changed or answer is not output, submit report WA, then I debug it, found value1 and value2 values ​​simply not right, explain the program start function value are wrong, then I useless pow function, but directly to pow (x, 3) expressed as x * x * x, re-export, actually AC. Also filed out, and then use the Internet Baidu pow function, this is my search to:

If the base x is negative and y is not an integer index, it will lead to error domain error. 
If the index base x and y are 0, it may result in an error domain error, or may not; this is related with the realization of the library. 
If the base x is 0, y index is negative, could result in domain error pole error or error, it may not; this is related with the realization of the library. 
If the return value ret is too big or too small, it will result in an error range error