二分法应用之解方程8x^4 + 7x^3 + 2x^2 + 3x + 6 NUSOJ 2671
Problem：
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：先输入t，代表有t个测试数据，然后输入测试的数也就是Y，然后根据8 * x^4 + 7 * x^3 + 2 * x^2 +3*x+ 6 = Y，求出x的值，很简单的二分题目。
#include<bits/stdc++.h> using namespace std; double vis(double y){ return 8*pow(y,4)+7*pow(y,3)+2*pow(y,2)+3*y+6; } int main() { int t; cin>>t; //t个测试数据 while(t--){ double y; cin>>y;//x在1~100之间，y不会超过807020306，不会小于6 if(y>807020306 || y<6) printf("langxinxuechang!\n"); else { double left=0,right=100,mid; while(right-left>0.000000001){ mid = left + (right-left)/2 ; if(vis(mid)==y) break; else if(vis(mid)>y) right = mid; else if(vis(mid)<y) left = mid; } printf("%.4f\n",mid); } } return 0; }