HDU 2199 Can you solve this equation?(二分)
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2024-03-17 15:22:34
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Can you solve this equation?
Now,given the equation 8x^4 + 7x^3 + 2x^2 + 3x + 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!
题意:
题意很简单,就是让你求在0~100的实数范围内方程是否有解
思路:
先判断是否有解,在有解的情况下进行二分,二分的时候考虑一下精度,精度的话我是到1e-8过了
#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<iostream>
#include<math.h>
#include<queue>
using namespace std;
const int inf=0x3f3f3f3f;
double solve(double x)
{
return 8*pow(x,4.0)+7*pow(x,3.0)+2*pow(x,2.0)+3*x+6;
}
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
double y;
scanf("%lf",&y);
if(y<solve(0.0)||y>solve(100.0)) //无解
{
printf("No solution!\n");
}
else
{
double l=0,r=100,mid,ans;
while(r-l>1e-8)
{
mid=(l+r)/2;
ans=solve(mid);
if(ans>y)
{
r=mid;
}
else
{
l=mid;
}
}
printf("%.4lf\n",mid);
}
}
return 0;
}
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