Hexadecimal to Decimal

Problem: Convert the given hexadecimal string into decimal.

Example:


hex_to_decimal('198F')
6543

hex_to_decimal('19AF')

6575

Solution in Python:

def hex_to_decimal(hex_str):
    """
    Author: Mayur P Srivastava
    """

    decimal_number = 0

    n = len(hex_str)

    for i in range(n - 1, -1, -1):

        c = ord(hex_str[i])

        if c >= 65 and c <= 70:

            c = 10 + c - 65

        elif c >= 97 and c <= 102:

            c = 10 + c - 97

        elif c >= 48 and c <= 57:

            c = c - 48

        else:

            assert False

        decimal_number += 16**(n-i-1) * c

    return decimal_number

Concepts Learned: Single loop, number system.