我已尽力获取用户在单独列表中给出的任意多项式的幂和系数。
基本上，只使用系数部分而不是功率部分，但功率列表（变量的列表仅用于比较）。我已经完成它并且它可以工作，但代码有点草率和非优雅。有没有更好的方法来编码？
基本上应该做的是：
当用户输入说：4x3+3时，它应该返回如下内容：
coeffs = [4,0,0,3]
这样我就可以用Horner的方法求解多项式。
以下是可运行的代码：REPL CODE
使用测试函数运行代码：
x = solve(function)
x.parse()
#!/usr/bin/python3
######################################################################
#code information
#
#
# When the user provides the input of the form
# 4x3+2x+1
# The parse method is expected to return
# A coefficient list of the provided polynomial
# in ready for use for the horner's method of solving
#######################################################################
function = "4x3+2x+1" #this is the sample input the user is expected to give
#
class solve:
def __init__(self, string):
self.function = string
self.letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g',
'h', 'i', 'j', 'k', 'l', 'm', 'n',
'o', 'p', 'q', 'r', 's', 't', 'u',
'v', 'w', 'x', 'y', 'z']
#######################################################################
#######################################################################
#######################################################################
#######################################################################
def parse(self):
signs = ['+', '-', '*']
for sign in signs:
self.function = self.function.replace(sign, ' ')#this is where all the
#signs are converted
#to spaces
self.function = self.function.split() #this is where all the
#list is split into terms
self.function.sort(reverse = True) #the polynomial is sorted always
#in the decreasing order
#from higher to lower order of x
coeffs = [] #list that holds all the coefficients
powers = [] #list that holds all the powers
while self.function:
term = self.function.pop(0)#for each term in the polynomial
for letter in self.letters:
#check for the alphabets in the letters(The list above)
if letter in term:
x, y = term.split(letter)
coeffs.append(int(x))#append the coefficient to the list
if y != '':
powers.append(int(y))#append the power to the list
else:
powers.append(1) #append 1 for x ^ 1 term
else:
try:
temp = int(term) #exception occurs here
coeffs.append(temp)#append constant term after exhaution
#of all the polynomial terms
#if no constants exits
#this is not reached
#and neither the line
#directly below
powers.append(0)#only for a constant,we have power 0
break #break nonsense to append only once
except:
pass #exception passed silently
return self.check_complete(coeffs, powers)
print("The coefficients are: ", coeffs)
print("The powers are: ", powers)
#######################################################################
#######################################################################
#######################################################################
#######################################################################
def check_complete(self, coeffs, powers):
"""This function checks if the polynomial is a
complete polynomial that is if it has all the powers of x
it does this by comparing the two lists hand in hand,
that is checks the corresponding terms"""
try:
#while the function arrives here
#power and range are assumed to be of same length
factor = 0 #factor for keeping track of index below
for index in range(len(powers)):
########################################
########################################
Index = index + factor #just cleaning up
########################################
########################################
difference = powers[Index] - powers[Index+1]
while difference > 1:
factor += 1 #factor incremented to keep track
#of where to add
difference -= 1
coeffs.insert(Index+1, 0)#in the coefficient list
#insert zeros where the
#polynomial is missing a term
except:
return coeffs #pass the exception
答案 0 :(得分：1)
是的，你让这太复杂了。另外，我认为你在解析时犯了一个错误，因为你把所有的运算符看作是它们的补充：你把它们改成空格然后忽略差异。我测试了这个，但你没有提供MCVE。
我建议一些简单的步骤。考虑多项式1 + 4x3-2x。
["1", "+4x3", "-2x"]。["+1x0", "+4x3", "-2x1"]。[(1, 0), (4, 3), (-2, 1)]。代码：
size = max[z[1] for z in terms] + 1
coeff = [0]*size
for term in terms:
coeff[term[1]] = term[0]