How Can I Efficiently Convert Integers to Their Written Forms Without Using Lookup Tables?

Avoiding Lookup Tables: An Efficient Algorithm for Converting Integers to Words

Converting integers into their word representations is a common programming task. While lookup tables provide a simple solution for smaller numbers, they become unwieldy for larger values. This article presents a more scalable, efficient method that avoids the use of large lookup tables.

The core of this approach involves several arrays:

• ones: An array holding the words for single-digit numbers (e.g., "One", "Two", ... "Nine").
• teens: An array containing the words for numbers eleven through nineteen.
• tens: An array holding the words for multiples of ten (e.g., "Twenty", "Thirty", ... "Ninety").
• thousandsGroups: An array containing the prefixes for thousands, millions, and billions.

The algorithm's heart is the FriendlyInteger function, a recursive function taking three parameters:

• n: The integer to convert.
• leftDigits: The word representation of digits to the left of n (used for recursion).
• thousands: The current thousands group (units, thousands, millions, etc.).

FriendlyInteger recursively breaks down the input integer, building the word representation piece by piece. For instance, converting 1532:

1. FriendlyInteger(32, "One Thousand", 1): Processes the thousands place, resulting in "One Thousand".
2. FriendlyInteger(32, null, 0): Handles the remaining 32.
3. FriendlyInteger(2, "Thirty", 0): Processes the tens digit, generating "Thirty".
4. FriendlyInteger(0, "Two", 0): Handles the units digit, yielding "Two".
5. The final result is concatenated: "One Thousand Three Hundred Thirty-Two".

The IntegerToWritten function serves as the entry point, handling special cases like zero and negative numbers before calling FriendlyInteger for the main conversion.

This recursive approach, combined with the use of predefined arrays, provides an efficient and scalable solution for converting integers to their written forms without the need for extensive lookup tables, making it suitable for handling a wide range of numerical inputs.

The above is the detailed content of How Can I Efficiently Convert Integers to Their Written Forms Without Using Lookup Tables?. For more information, please follow other related articles on the PHP Chinese website!