Python: Get all possible two digit letter combinations from a digit string

Python Basic - 1: Exercise-13 with Solution

Two-Digit Letter Combos

Write a Python program to get all possible two-digit letter combinations from a 1-9 digit string.

string_maps = {
"1": "abc",
"2": "def",
"3": "ghi",
"4": "jkl",
"5": "mno",
"6": "pqrs",
"7": "tuv",
"8": "wxy",
"9": "z"
}

Visual Presentation:

Sample Solution:

Python Code:

# Define a function 'letter_combinations' that generates letter combinations based on input digits.
def letter_combinations(digits):
    # Check if the input string is empty.
    if digits == "":
        return []
    
    # Define a mapping of digits to corresponding letters.
    string_maps = {
        "1": "abc",
        "2": "def",
        "3": "ghi",
        "4": "jkl",
        "5": "mno",
        "6": "pqrs",
        "7": "tuv",
        "8": "wxy",
        "9": "z"
    }
    
    # Initialize the result list with an empty string.
    result = [""]
    
    # Iterate through each digit in the input string.
    for num in digits:
        # Create a temporary list to store new combinations.
        temp = []
        
        # Iterate through each existing combination in the result list.
        for an in result:
            # Append each letter corresponding to the current digit to create new combinations.
            for char in string_maps[num]:
                temp.append(an + char)
        
        # Update the result list with the new combinations.
        result = temp
    
    # Return the final list of letter combinations.
    return result

# Define input digit strings and print the corresponding letter combinations.
digit_string = "47"
print(letter_combinations(digit_string))
digit_string = "29"
print(letter_combinations(digit_string))

Sample Output:

['jt', 'ju', 'jv', 'kt', 'ku', 'kv', 'lt', 'lu', 'lv']
['dz', 'ez', 'fz']

Explanation:

The above Python code defines a function called "letter_combinations()" that generates letter combinations based on input digits. Here's a brief explanation:

• The function takes a string of digits ('digits') as input.
• If the input string is empty, it returns an empty list.
• It defines a mapping ('string_maps') of each digit to a string of corresponding letters.
• It initializes a result list with an empty string.
• It iterates through each digit in the input string.
• For each existing combination in the result list, it appends each letter corresponding to the current digit to create new combinations.
• It updates the result list with new combinations.
• The function returns the final list of letter combinations.

Flowchart:

Python Code Editor :

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