hdu 2899 Strange fuction
2015-08-31 20:14
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http://acm.hdu.edu.cn/showproblem.php?pid=2899
Total Submission(s): 4865 Accepted Submission(s): 3468
[align=left]Problem Description[/align]
Now, here is a fuction:
F(x) = 6 * x^7+8*x^6+7*x^3+5*x^2-y*x (0 <= x <=100)
Can you find the minimum value when x is between 0 and 100.
[align=left]Input[/align]
The first line of the input contains an integer T(1<=T<=100) which means the number of test cases. Then T lines follow, each line has only one real numbers Y.(0 < Y <1e10)
[align=left]Output[/align]
Just the minimum value (accurate up to 4 decimal places),when x is between 0 and 100.
[align=left]Sample Input[/align]
2
100
200
[align=left]Sample Output[/align]
-74.4291
-178.8534
二分搜索+求导
对函数进行求导,导数为0时,x的值是函数值最小
导数小于0函数递减,导数大于0函数递增
Strange fuction
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 4865 Accepted Submission(s): 3468
[align=left]Problem Description[/align]
Now, here is a fuction:
F(x) = 6 * x^7+8*x^6+7*x^3+5*x^2-y*x (0 <= x <=100)
Can you find the minimum value when x is between 0 and 100.
[align=left]Input[/align]
The first line of the input contains an integer T(1<=T<=100) which means the number of test cases. Then T lines follow, each line has only one real numbers Y.(0 < Y <1e10)
[align=left]Output[/align]
Just the minimum value (accurate up to 4 decimal places),when x is between 0 and 100.
[align=left]Sample Input[/align]
2
100
200
[align=left]Sample Output[/align]
-74.4291
-178.8534
二分搜索+求导
对函数进行求导,导数为0时,x的值是函数值最小
导数小于0函数递减,导数大于0函数递增
#include<stdio.h> #include<string.h> #include<stdlib.h> #include<math.h> #include<algorithm> #define N 1010 #define INF 0x3f3f3f3f using namespace std; int main() { int t; double y, f, f1; scanf("%d", &t); while(t--) { scanf("%lf", &y); double mid, low = 0, high = 100; while(high - low > 1e-8)/***此处注意*/ { mid = (low + high) / 2; f1 = 42 * pow(mid, 6) + 48 * pow(mid, 5) + 21 * pow(mid, 2) + 10 * mid;//导数 if(f1 < y) low = mid; else if(f1 == y) break; else high = mid; } f = 6 * pow(mid, 7) + 8 * pow(mid, 6) + 7 * pow(mid, 3) + 5 * pow(mid, 2) - mid * y; printf("%.4f\n", f); } return 0; }
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