Program to find number of different integers in a string using Python

When working with alphanumeric strings, we often need to extract and count distinct integers. This involves replacing non-digit characters with spaces and identifying unique numbers, where leading zeros don't affect the integer value.

Given a lowercase alphanumeric string, we need to replace every non-digit character with a space, leaving integers separated by spaces. Two numbers are considered the same if their decimal representations without leading zeros are identical.

Example

If the input string is s = "ab12fg012th5er67", we extract numbers ["12", "012", "5", "67"]. Since "12" and "012" represent the same integer value, we have 3 distinct integers: 12, 5, and 67.

Algorithm

The approach follows these steps ?

• Create an empty list to store extracted numbers

• Use a temporary string to build each number

• Iterate through each character in the string

• If character is a digit (ASCII 48-57), add it to temporary string

• If character is not a digit and temporary string is not empty, convert to integer and add to list

• Return count of unique integers using a set

Implementation

def solve(s):
    nums = []
    k = ""
    for i in range(len(s)):
        if ord(s[i]) > 47 and ord(s[i]) < 58:
            k += s[i]
        else:
            if k != "":
                nums.append(int(k))
                k = ""
    if k != "":
        nums.append(int(k))
    return len(set(nums))

s = "ab12fg012th5er67"
print(solve(s))

The output of the above code is ?

3

Alternative Approach Using Regular Expressions

We can simplify the solution using Python's re module to extract all digit sequences ?

import re

def solve_regex(s):
    numbers = re.findall(r'\d+', s)
    unique_integers = set(int(num) for num in numbers)
    return len(unique_integers)

s = "ab12fg012th5er67"
print(solve_regex(s))
print("Extracted numbers:", re.findall(r'\d+', s))
print("Unique integers:", set(int(num) for num in re.findall(r'\d+', s)))

3
Extracted numbers: ['12', '012', '5', '67']
Unique integers: {67, 5, 12}

How It Works

The algorithm processes each character and builds numbers digit by digit. When a non-digit character is encountered, the accumulated number string is converted to an integer, which automatically removes leading zeros. Using a set ensures only unique integers are counted.

Conclusion

Both approaches effectively count distinct integers in a string by extracting digit sequences and converting them to integers. The regular expression method provides cleaner code, while the character-by-character approach offers more control over the parsing process.