Number to Words - Problem

Write a function that converts a number (0-9999) to its English word representation. You must use helper functions to break down the problem into smaller parts.

Requirements:

Handle numbers from 0 to 9999
Return the English words with proper capitalization (first letter uppercase)
Use helper functions for different number ranges (ones, tens, hundreds, thousands)
No leading/trailing spaces in the result

Examples:

0 → "Zero"
42 → "Forty two"
1234 → "One thousand two hundred thirty four"

Input & Output

Example 1 — Basic Single Digit

$ Input: num = 0

› Output: Zero

💡 Note: Special case: zero is handled separately and returns 'Zero' with capital Z

Example 2 — Two Digit Number

$ Input: num = 42

› Output: Forty two

💡 Note: 42 = 40 + 2, so we combine getTens(4)→'forty' with getOnes(2)→'two' to get 'Forty two'

Example 3 — Four Digit Number

$ Input: num = 1234

› Output: One thousand two hundred thirty four

💡 Note: 1234 = 1×1000 + 2×100 + 3×10 + 4×1. We convert each part: 'One thousand' + 'two hundred' + 'thirty four'

Constraints

0 ≤ num ≤ 9999
Return string with first letter capitalized
No leading or trailing spaces

Visualization

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Asked in

G Google 15 M Microsoft 12 a Amazon 8

The key insight is breaking the number into place values (thousands, hundreds, tens, ones) and using helper functions to convert each part. The optimal approach uses modular helper functions for clean, maintainable code. Time: O(1), Space: O(1)

Common Approaches

✓ Brute Force - Massive If-Else Chain

⏱️ Time: O(1) Space: O(n)

Create individual cases for every single number from 0 to 9999. This means writing out or storing 10,000 different string mappings, making the code extremely long and unmaintainable.

Helper Functions Approach

⏱️ Time: O(1) Space: O(1)

Use dedicated helper functions to convert different parts of the number. Extract thousands, hundreds, tens, and ones digits, then use appropriate helper functions to convert each part to words and combine them.

Brute Force - Massive If-Else Chain — Algorithm Steps

Create if-else chain or array with 10,000 entries
Look up the exact number
Return the corresponding word

Visualization

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Step-by-Step Walkthrough

Create Map

Store 10,000 number-to-word mappings

Lookup

Find exact number in the map

Return

Return the stored word

Code -

solution.c — C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char* solution(int num) {
    // Brute force: use switch for some cases (abbreviated)
    static char result[100];
    switch(num) {
        case 0: strcpy(result, "Zero"); break;
        case 1: strcpy(result, "One"); break;
        case 2: strcpy(result, "Two"); break;
        case 3: strcpy(result, "Three"); break;
        case 10: strcpy(result, "Ten"); break;
        case 20: strcpy(result, "Twenty"); break;
        case 100: strcpy(result, "One hundred"); break;
        case 1000: strcpy(result, "One thousand"); break;
        case 1234: strcpy(result, "One thousand two hundred thirty four"); break;
        // ... would need 10,000 cases total
        default: strcpy(result, "Unknown"); break;
    }
    return result;
}

int main() {
    int num;
    scanf("%d", &num);
    char* result = solution(num);
    printf("%s\n", result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Direct lookup by index or single if-else comparison

✓ Linear Growth

Space Complexity

O(n)

Need to store 10,000 string mappings in memory

⚡ Linearithmic Space

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Number to Words - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Brute Force - Massive If-Else Chain — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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