Integer to English Words

Integer to English Words - Problem

Convert a non-negative integer num to its English words representation.

Example: Given num = 123, return "One Hundred Twenty Three"

Note: You need to handle numbers from 0 to 2,147,483,647 (2³¹ - 1)

The output should be properly capitalized with spaces between words, and no extra spaces at the beginning or end.

Input & Output

Example 1 — Basic Case

$ Input: num = 123

› Output: One Hundred Twenty Three

💡 Note: 123 = 1 hundred + 20 + 3 → One Hundred Twenty Three

Example 2 — Edge Case Zero

$ Input: num = 0

› Output: Zero

💡 Note: Special case: zero is handled separately

Example 3 — Large Number

$ Input: num = 1234567

› Output: One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven

💡 Note: Break into groups: 1 million + 234 thousand + 567

Constraints

0 ≤ num ≤ 2³¹ - 1
The input is guaranteed to be a valid integer

Visualization

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Asked in

M Microsoft 45 F Facebook 38 A Amazon 32 G Google 28

The key insight is to break numbers into groups of thousands (billions, millions, thousands, ones) and handle each group recursively. The optimal approach uses divide and conquer with recursion to process each group separately. Time: O(log n), Space: O(log n)

Common Approaches

✓ Hash Map

⏱️ Time: N/A Space: N/A

Brute Force - Giant Lookup Table

⏱️ Time: O(1) Space: O(1)

Handle every possible number combination with extensive if-else statements and huge arrays. This would require storing thousands of pre-computed strings.

Divide and Conquer with Recursion

⏱️ Time: O(log n) Space: O(log n)

Divide the number by powers of 1000 (billions, millions, thousands) and recursively convert each group. Use helper arrays for basic number words and combine results.

Algorithm Steps — Algorithm Steps

Code -

solution.c — C

Time & Space Complexity

Time Complexity

⏱️

✓ Linear Growth

Space Complexity

✓ Linear Space

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Smart Actions

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