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杭电 HDU ACM 2199 Can you solve this equation?

栏目:php教程时间:2015-05-08 07:46:43

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 11180    Accepted Submission(s): 5151


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 ⑷
 

Sample Output
1.6152 No solution!
 

Author
Redow
 
 
搜索题,嗯, 这次知道了有个搜索名次,2分搜索。这样查找答案确切感觉特别妙。low 和high 无穷夹逼答案。所以由于最后结果只需满足1定的精确度。这样可以找到适合的条件跳出while。
唉,如果不知道这样的话,浮点数暴力简直无语了都。
#include<iostream> #include<cmath> #include<stdio.h> using namespace std; double A(double x) { return (8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*pow(x,1)+6); } int main() { double y; int T; cin>>T; while(T--) { cin>>y; if(A(0)>y||A(100)<y) { cout<<"No solution!"<<endl; continue; } else{ double high,low,mid; high=100; low=0; while(low+1e⑻<high) { mid=(high+low)/2; if(A(mid)>y) high=mid; else low=mid; } printf("%.4lf ",low); } } return 0; }

 
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