Ramiro N. Cosa

Thermostat Adjuster - FreeCodeCamp #36 Daily Challenge

2 min

Thermostat Adjuster - Analysis and Explanation

Problem Statement

Given the current temperature of a room and a target temperature, the goal is to return a string indicating how to adjust the thermostat based on the following rules:

  • Return "heat" if the current temperature is less than the target temperature.
  • Return "cool" if the current temperature is greater than the target temperature.
  • Return "hold" if the current temperature is equal to the target temperature.

Initial Analysis

Understanding the Problem

The problem requires implementing the basic logic of a thermostat. We must compare two numerical values (temp and target) and return an action instruction. It is a fundamental exercise for practicing conditional control structures and numerical comparisons.

Logic Visualization

flowchart TD
  A["Start: temp, target"] --> B{"temp < target?"}
  B -- "Yes" --> C["Result: 'heat'"]
  B -- "No" --> D{"temp > target?"}
  D -- "Yes" --> E["Result: 'cool'"]
  D -- "No" --> F["Result: 'hold'"]

Identified Test Cases

  1. Heat: temp < target (e.g., 68<7268 < 72) →\rightarrow "heat".
  2. Cool: temp > target (e.g., 75>7275 > 72) →\rightarrow "cool".
  3. Hold: temp === target (e.g., 72===7272 === 72) →\rightarrow "hold".
  4. Negative Numbers: The logic must be consistent even at sub-zero temperatures.
  5. Decimals: The comparison must handle floating-point numbers accurately.

Solution Development

Chosen Approach

The most direct and readable approach is to use an if...else if...else control structure. Since the three conditions are mutually exclusive, this structure allows for a clear and efficient execution flow.

Implementation

/**
 * Adjusts the thermostat by comparing the current temperature with the target.
 * @param temp Current temperature.
 * @param target Desired temperature.
 * @returns Action to perform: 'heat', 'cool', or 'hold'.
 */
function adjustThermostat(temp: number, target: number): string {
  if (temp < target) {
    return 'heat'
  }
  else if (temp > target) {
    return 'cool'
  }
  else {
    return 'hold'
  }
}

Complexity Analysis

Time Complexity

O(1)O(1). The function performs a constant number of comparisons (maximum 2) regardless of the magnitude of the input values.

Space Complexity

O(1)O(1). No additional memory is used that depends on the input size; only a predefined string literal is returned.

Edge Cases and Considerations

  • Floating-point precision: In JavaScript/TypeScript, decimal number comparisons are direct. Although critical systems often use a margin of error (epsilon), for this challenge, we assume strict equality.
  • Extreme values: The logic correctly handles very high, very low, or absolute zero values.

Reflections and Learnings

Applied Concepts

  • Control Structures: Use of conditionals for logical decision-making.
  • Early Returns: Although we use else if, the structure allows returning as soon as a condition is met, avoiding unnecessary evaluations.

Concise Alternative

We could use a chained ternary operator to reduce lines, although in physical device logic, the clarity of if is usually preferred:

function adjustThermostat(temp: number, target: number): string {
  return temp < target ? 'heat' : temp > target ? 'cool' : 'hold'
}

Resources and References

freecodecamp daily-challenge