11_string_to_integer.py

'''
You are given some numeric string as input. Convert the string you are
given to an integer. Do not make use of the built-in "int" function.
Example:
    "123" : 123
    "-12332" : -12332
    "554" : 554
    etc.
'''

def str_to_int(input_str):
    
    output_int = 0

    if input_str[0] == '-':
        start_idx = 1
        is_negative = True
    else:
        start_idx = 0
        is_negative = False

    for i in range(start_idx, len(input_str)):
        # print(len(input_str))
        # print(i)
        place = 10**(len(input_str) - (i+1))
        digit = ord(input_str[i]) -ord('0')
        output_int += place * digit

    if is_negative:
        return -1 * output_int
    else:
        return output_int

    
def myAtoi(str: str) -> int:
    str = str.strip()

    if not str:
        return 0
    
    negative = False
    output_int = 0

    if str[0] == '-':
        negative = True
    elif str[0] == '+':
        negative = False
    elif not str[0].isnumeric():
        return 0
    else:
        output_int = ord(str[0]) - ord('0')
    
    for i in range(1, len(str)):
        if str[i].isnumeric():
            output_int = output_int*10 + (ord(str[i]) - ord('0'))
            if not negative and output_int >= 2147483648:
                return 2147483647
            if negative and output_int >= 2147483648:
                return -2147483648
        else:
            break
    
    if not negative:
        return output_int
    else:
        return -output_int



if __name__ == "__main__":
    
    str_1 = "123"
    X = str_to_int(str_1)
    print(X)
    print(type(X))
    print("\n")

    str_2 = "-123"
    Y = str_to_int(str_2)
    print(Y)
    print(type(Y))
    print("\n")

    str_3 = "554"
    Z = str_to_int(str_3)
    print(Z)
    print(type(Z))
    print("\n")

    str_4 = "42"
    A = myAtoi(str_4)
    print(A)
    print(type(A))
    print("\n")

    str_5 = "   -42"
    B = myAtoi(str_5)
    print(B)
    print(type(B))
    print("\n")

    str_6 = "4193 with words"
    C = myAtoi(str_6)
    print(C)
    print(type(C))
    print("\n")

    str_7 = "words and 987"
    D = myAtoi(str_7)
    print(D)
    print(type(D))
    print("\n")