How do you split an integer into an array?

To split an integer into an array, the most common and straightforward method is to convert the integer into its string representation, then separate each character, and finally convert each character back into a numerical digit. This process effectively breaks down the number into an array of its individual digits.

The String Conversion Method

This approach leverages the flexibility of string manipulation to parse the integer digit by digit. It's generally the most intuitive and widely used method across various programming languages.

Step-by-Step Process

1. Convert to String: Transform the integer into its string equivalent. This allows you to treat the number as a sequence of characters.
2. Split the String: Break the string into an array of individual characters. Each character will correspond to a digit of the original number.
3. Convert to Number: Iterate through the array of character-digits and convert each character back into a numeric value.

Here's a visual representation of the process:

Example (JavaScript)

function splitIntegerToArrayString(number) {
  // Convert the number to a string
  const numString = String(number);

  // Split the string into an array of characters
  const charArray = numString.split('');

  // Convert each character back to a number
  const digitArray = charArray.map(Number);

  return digitArray;
}

console.log(splitIntegerToArrayString(12345)); // Output: [1, 2, 3, 4, 5]
console.log(splitIntegerToArrayString(709));   // Output: [7, 0, 9]

Example (Python)

def split_integer_to_array_string(number):
  # Convert the number to a string
  num_string = str(number)

  # Split the string (which already works character by character)
  # and convert each character to an integer
  digit_array = [int(digit) for digit in num_string]

  return digit_array

print(split_integer_to_array_string(12345)) # Output: [1, 2, 3, 4, 5]
print(split_integer_to_array_string(709))   # Output: [7, 0, 9]

The Mathematical Method

For scenarios where string conversion might be less efficient or desirable (e.g., in performance-critical applications or languages without easy string-to-number conversion utilities), a mathematical approach can be used. This method relies on the modulo (%) and integer division (//) operators.

Step-by-Step Process

1. Initialize Array: Create an empty array to store the digits.
2. Loop: While the number is greater than 0, repeat the following steps:
   • Extract Last Digit: Use the modulo operator (% 10) to get the last digit of the number.
   • Add to Array: Add this digit to the array. Note: If adding to the end, the array will be in reverse order of the digits, so it may need to be reversed at the end.
   • Remove Last Digit: Use integer division (// 10) to remove the last digit from the number.
3. Reverse (if necessary): If digits were added to the end of the array, reverse the array to get the correct order.

Example (JavaScript)

function splitIntegerToArrayMath(number) {
  if (number === 0) return [0]; // Special case for zero
  if (number < 0) number = Math.abs(number); // Handle negative numbers

  const digitArray = [];
  while (number > 0) {
    const lastDigit = number % 10; // Get the last digit
    digitArray.unshift(lastDigit); // Add to the beginning of the array
    number = Math.floor(number / 10); // Remove the last digit (integer division)
  }
  return digitArray;
}

console.log(splitIntegerToArrayMath(12345)); // Output: [1, 2, 3, 4, 5]
console.log(splitIntegerToArrayMath(709));   // Output: [7, 0, 9]
console.log(splitIntegerToArrayMath(0));     // Output: [0]
console.log(splitIntegerToArrayMath(-567));  // Output: [5, 6, 7]

Example (Python)

def split_integer_to_array_math(number):
  if number == 0:
    return [0]
  if number < 0:
    number = abs(number) # Handle negative numbers

  digit_array = []
  while number > 0:
    last_digit = number % 10 # Get the last digit
    digit_array.insert(0, last_digit) # Add to the beginning of the list
    number = number // 10 # Remove the last digit (integer division)
  return digit_array

print(split_integer_to_array_math(12345)) # Output: [1, 2, 3, 4, 5]
print(split_integer_to_array_math(709))   # Output: [7, 0, 9]
print(split_integer_to_array_math(0))     # Output: [0]
print(split_integer_to_array_math(-567))  # Output: [5, 6, 7]

Handling Negative Numbers and Zero

Both methods can be adapted to handle negative integers and the number zero:

• String Conversion: When converting a negative number to a string, the minus sign (-) will be included. You can typically remove this sign before splitting and then apply the conversion. For example, String(-123) becomes "-123". You might need to check if the first character is a - and handle it accordingly, usually by taking the absolute value before conversion or filtering out non-digit characters.
• Mathematical Method: For negative numbers, take their absolute value first (abs(number) or Math.abs(number)). For zero, the loop condition number > 0 will not be met, so a special if number == 0 check is required to return [0].

In most programming contexts, the string conversion method is preferred for its simplicity and readability when the primary goal is to split an integer into its digits.