Solve For X
Codewars Kata 40√
Description
Link:
https://www.codewars.com/kata/59c2e2a36bddd2707e000079/solutions/python
-简述：本题给定一个方程式形式的字符串，求方程的解。
-思路：运用eval()函数，直接求解字符串形式的方程。
-难点：1 没有难点~
You will be given an equation as a string and you will need to solve for X(https://www.mathplacementreview.com/algebra/basic-algebra.php#solve-for-a-variable)
and return x’s value. For example:
solve_for_x(‘x - 5 = 20’) # should return 25
solve_for_x(‘20 = 5 * x - 5’) # should return 5
solve_for_x(‘5 * x = x + 8’) # should return 2
solve_for_x(‘(5 - 3) * x = x + 2’) # should return 2
NOTES:
-All numbers will be whole numbers
-Don’t forget about the order of operations.https://www.mathplacementreview.com/algebra/basic-algebra.php#order-of-operations
-If the random tests don’t pass the first time, just run them again.
My solution
def solve_for_x(equation):
for x in range(-1000,1001):
if eval(equation.replace('=','==')):
return x
print(solve_for_x('2*x+1=5'))
Given solutions
from itertools import count
def solve_for_x(equation):
return next( x for n in count(0) for x in [n, -n] if eval(equation.replace("x", str(x)).replace("=", "==")) )
def solve_for_x(equation):
left_side = equation.split('=')[0];
right_side = equation.split('=')[1];
for x in range(-1000, 1000):
if eval(left_side) == eval(right_side):
return x
Points
1 函数next()，它通过调用其next ()方法从迭代器中检索下一个项目。
2 count(0) 是所有整数的序列。
