[python]Binomial Expansion

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저는 정규표현식을 사용하지 않았지만 정규표현식을 사용하면 코드 길이는 훨씬 짧아질 것 같습니다.

 

코드를 보시려면 더보기를 클릭하시면 됩니다.

Binomial Expansion

# My Code
def expand(expr):
    tmp = expr.replace('(', '').replace(')', '').split('^')
    if tmp[1] == str(0):
        return str(1)
    elif tmp[1] == str(1):
        return tmp[0]
    else:
        # c 추출
        c = int(tmp[1])
 
        # 제곱시에 필요한 상수 값
        tmp_b = [[] for _ in range(c + 1)]
        tmp_b[0] = [1, 1]
        for i in range(1, len(tmp_b)):
            tmp_b[i].append(1)
            for j in range(i-1):
                tmp_b[i].append(tmp_b[i-1][j]+tmp_b[i-1][j+1])
            tmp_b[i].append(1)
 
        x = ''
        x_index = 0
 
        # x 추출
        for i in tmp[0]:
            if 'a' <= i <= 'z' or 'A' <= i <= 'Z':
                x_index = tmp[0].find(i)
                x = tmp[0][x_index]
                break
 
        # a 추출
        a = tmp[0][:x_index]
        if a == '-':
            a = int(-1)
        elif a == '':
            a = int(1)
        else:
            a = int(tmp[0][:x_index])
 
        # b 추출
        b = int(tmp[0][x_index + 1:])
 
        cnt = c
        answer_list = []
        for i in tmp_b[-1]:
            a_tmp = i * pow(a, cnt) * pow(b, c-cnt)
 
            if cnt == 0:
                answer_list.append(str(a_tmp))
            elif cnt == 1:
                answer_list.append(str(a_tmp) + x)
            else:
                if a_tmp == 1:
                    answer_list.append(x + '^' + str(cnt))
                elif a_tmp == -1:
                    answer_list.append('-' + x + '^' + str(cnt))
                else:
                    answer_list.append(str(a_tmp) + x + '^' + str(cnt))
            cnt -= 1
 
        answer = answer_list[0]
        for i in range(1, len(answer_list)):
            if answer_list[i][0] == '-':
                answer += answer_list[i]
            else:
                answer += ('+' + answer_list[i])
 
    return answer
 
if __name__=='__main__':
    print(expand("(x-1)^0"))
    print(expand("(x-1)^1"))
    print(expand("(x-1)^2"))
    print(expand("(5m+3)^4"))
    print(expand("(2x-3)^3"))
    print(expand("(7x-7)^0"))