hdu 2199 Can you solve this equation?
2015-11-19 08:51
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Can you solve this equation?
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 13855 Accepted Submission(s): 6185
Problem Description
Now,given the equation 8*x^4 + 7*x^3 + 2*x^2 + 3*x + 6 == Y,can you find its solution between 0 and 100;
Now please try your lucky.
Input
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 a real number Y (fabs(Y) <= 1e10);
Output
For each test case, you should just output one real number(accurate up to 4 decimal places),which is the solution of the equation,or “No solution!”,if there is no solution for the equation between 0 and 100.
Sample Input
2
100
-4
Sample Output
1.6152
No solution!题型:二分查找注意,,double型数据不能直接用等号,而应该作使差的绝对值小于一个足够小的数,,水题#include<iostream>
#include<cstdio>
#include<cstring>
#include<math.h>
using namespace std;
double y;
double f(double x)
{
return 8*x*x*x*x+7*x*x*x+2*x*x+3*x+6-y;
}
int main()
{
int cas;
scanf("%d",&cas);
while(cas--)
{
scanf("%lf",&y);
if(f(0)>0||f(100)<0)
{
printf("No solution!\n");
continue;
}
double m,l=0,r=100;
while(r-l>=1e-8)
{
m=(l+r)/2.0;
if(f(m)<0)
l=m;
else
r=m;
if(fabs(f(m))<1e-8)
break;
}
printf("%.4lf\n",m);
}
return 0;
}
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