# 5 Best Ways to Determine the Length of Concatenated Unique Character Strings in Python

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π‘ Problem Formulation: This article addresses the challenge of calculating the length of a concatenated string that’s composed uniquely of characters from multiple input strings without any repetition. Given two strings, e.g., ‘apple’ and ‘pear’, a valid concatenated unique character string would be ‘apler’, and the desired output is the length: 5.

## Method 1: Using a Loop to Create a Unique Character String

This method involves iterating over each character in the input strings and adding it to a new string if it’s not already present. This approach is straightforward and easy to understand for beginners but may not be the most efficient for longer strings.

Here’s an example:

```def unique_concat(str1, str2):
result = ""
for char in str1 + str2:
if char not in result:
result += char
return len(result)

print(unique_concat("apple", "pear"))```

The output of this code snippet is:

`5`

This method concatenates the two input strings and loops through each character, appending unique characters to a new string. Finally, it returns the length of this string. It’s intuitive but may be slower for long inputs due to its linear complexity with respect to the total length of the input strings.

## Method 2: Using Set to Find Unique Characters

By converting the input strings into sets, Python automatically removes duplicate characters. Concatenating the sets and converting back to a string provides the unique character string, and its length can be easily computed. This method is more efficient due to the nature of sets in Python.

Here’s an example:

```def unique_length_with_sets(str1, str2):
return len(set(str1 + str2))

print(unique_length_with_sets("apple", "pear"))```

The output of this code snippet is:

`5`

In this snippet, both strings are concatenated, and a set is created to eliminate duplicates. The length of the resulting set represents the number of unique characters. This method is efficient but loses the original order of characters.

## Method 3: Using Dictionary Comprehension

Dictionary comprehension in Python can be used to track the occurrence of characters. Since dictionary keys are unique, this method is useful for creating a collection of unique characters. This method maintains character order and is more efficient than looping.

Here’s an example:

```def unique_length_with_dict(str1, str2):
unique_chars = {char: None for char in str1 + str2}
return len(unique_chars)

print(unique_length_with_dict("apple", "pear"))```

The output of this code snippet is:

`5`

This code utilizes dictionary comprehension to keep track of unique characters. The length of the dictionary’s keys provides the count of unique characters. This approach preserves the original character order and is more efficient than a naive loop.

## Method 4: Functional Approach with `reduce()` and `set()`

The functional programming approach makes use of the `reduce()` function to accumulate unique characters across multiple strings. This is a more advanced method that’s best for those comfortable with functional programming concepts.

Here’s an example:

```from functools import reduce

def unique_length_functional(*args):
return len(reduce(lambda acc, x: set(acc) | set(x), args, ""))

print(unique_length_functional("apple", "pear"))```

The output of this code snippet is:

`5`

This snippet takes advantage of the `reduce()` function to combine sets of characters from each string. The union operation ensures that only unique characters are counted. While elegant, this method may be less intuitive for those unfamiliar with functional programming.

## Bonus One-Liner Method 5: Using `len()` and `set()` in a Single Expression

For a succinct solution, Python’s ability to perform operations in a single line can be leveraged. This one-liner combines the operation of creating sets and getting the length in a compact and readable format.

Here’s an example:

`print(len(set("apple" + "pear")))`

The output of this code snippet is:

`5`

This code creates a set from the concatenated input strings to remove duplicates, and the `len()` function is immediately called to get the count of unique characters. This one-liner is the epitome of Python’s capability for writing concise and efficient code.

## Summary/Discussion

• Method 1: Loop and Concatenation. Simple for beginners. Potentially slow for long strings.
• Method 2: Set Conversion. Efficient and clean. Loses original character order.
• Method 3: Dictionary Comprehension. Efficient and maintains order. Slightly more complex syntax.
• Method 4: Functional with `reduce()`. Elegant and efficient. Less intuitive for some users.
• Method 5: One-Liner. Extremely concise. Excellent for quick tasks but may lack readability for complex operations.