Speed Limit - FreeCodeCamp #127 Daily Challenge

Problem Statement

Given a speed in miles per hour (MPH) and a limit in kilometers per hour (KPH):

• If your speed (converted to KPH) is less than or equal to the limit, return “Not Speeding”.
• If you exceed the limit by up to 5 KPH, return “Warning”.
• If you exceed the limit by more than 5 KPH, return “Ticket”.

Useful fact: $1$ mile = $1.60934$ kilometers.

🔍 Initial Analysis

Before coding, let’s clarify the decision flow:

flowchart TD
  A["Speed in MPH"] --> B["Convert to KPH"]
  B --> C{"speedKPH ≤ limit?"}
  C -- Yes --> D["Not Speeding"]
  C -- No --> E{"≤ limit + 5?"}
  E -- Yes --> F["Warning"]
  E -- No --> G["Ticket"]

Key Test Cases

• Case 1: Speed within the limit
  • Input: speedMph = 30, speedLimitKph = 70
  • Expected Output: “Not Speeding”
• Case 2: Speed with warning
  • Input: speedMph = 40, speedLimitKph = 60
  • Expected Output: “Warning”
• Case 3: Speed right at the warning threshold
  • Input: speedMph = 40, speedLimitKph = 65
  • Expected Output: “Not Speeding”
• Case 4: Speed with ticket
  • Input: speedMph = 60, speedLimitKph = 90
  • Expected Output: “Ticket”
• Case 5: Speed with warning near the limit
  • Input: speedMph = 65, speedLimitKph = 100
• Expected Output: “Warning”
• Case 6: Speed far above the limit
  • Input: speedMph = 88, speedLimitKph = 40
  • Expected Output: “Ticket”

🛠️ Solution Development

Strategy

1. Convert units: $speedKPH = speedMph \times 1.60934$

2. Compare with the limit:

• If $speedKPH \leq speedLimitKph$ → “Not Speeding”
• If $speedKPH \leq speedLimitKph + 5$ → “Warning”
• If $speedKPH > speedLimitKph + 5$ → “Ticket”

JavaScript Implementation

function speedCheck(speedMph, speedLimitKph) {
  const speedKPH = speedMph * 1.60934
  if (speedKPH <= speedLimitKph)
    return 'Not Speeding'
  if (speedKPH <= speedLimitKph + 5)
    return 'Warning'
  return 'Ticket'
}

⚡ Complexity Analysis

• Time: $O(1)$
• Space: $O(1)$

🧩 Edge Cases and Considerations

• If the speed is equal to the limit → “Not Speeding”
• If it is exactly 5 KPH above → “Warning”
• Negative or zero speed → “Not Speeding” (not realistic, but the code allows it)
• Precision depends on the conversion factor ($1.60934$)

💡 Reflections and Learnings

What did we learn?

• Unit conversion
• Thinking about edge cases

📚 Resources and References

• Miles to kilometers conversion - Wikipedia
• freeCodeCamp Daily Coding Challenge