Ramiro N. Cosa

Screen Time - FreeCodeCamp #33 Daily Challenge

2 min

Problem Statement

Given an array of seven integers, each representing the number of hours spent on your phone per day in a week, determine if the screen time is excessive based on these criteria:

  • If any day has 10 or more hours, it’s too much.
  • If the average of any three consecutive days is 8 hours or more, it’s too much.
  • If the weekly average is 6 hours or more, it’s too much.

Analysis & Strategy

If any condition is met, the function should return true. The problem is solved with three checks:

  1. Is there any day with 10+ hours?
  2. Does any consecutive trio average 8+ hours?
  3. Is the weekly average 6+ hours?

Test Cases

  1. [1, 2, 3, 4, 5, 6, 7] → false
    • No day exceeds 10 hours, no trio averages 8+, and the weekly average is below 6.
  2. [7, 8, 8, 4, 2, 2, 3] → false
    • No day with 10+, no trio averages 8+, weekly average below 6.
  3. [5, 6, 6, 6, 6, 6, 6] → false
    • No day with 10+, no trio averages 8+, weekly average below 6.
  4. [1, 2, 3, 11, 1, 3, 4] → true
    • Day 4 has 11 hours (condition 1).
  5. [1, 2, 3, 10, 2, 1, 0] → true
    • Day 4 has 10 hours (condition 1).
  6. [3, 3, 5, 8, 8, 9, 4] → true
    • Trio [8, 8, 9] averages 8.33 (condition 2).
  7. [3, 9, 4, 8, 5, 7, 6] → true
    • Weekly average is 6 (condition 3).

Edge cases:

  • [0, 0, 0, 0, 0, 0, 0] → false
    • No day or average exceeds the limits.
  • [6, 6, 6, 6, 6, 6, 6] → true
    • Weekly average is exactly 6 (condition 3).
  • [8, 8, 8, 1, 1, 1, 1] → true
    • The initial trio averages 8 (condition 2).

Solution Development

We use a sliding window for moving averages and short-circuit as soon as a condition is met. Everything can be done in a single pass through the array. The approach is:

  1. Check if any day has 10 or more hours.
  2. Calculate averages for every three consecutive days.
  3. Calculate the weekly average.
  4. Return true if any condition is met, otherwise false.

Decision Diagram

flowchart TD
  A["Any day ≥ 10h?"] -- Yes --> T["Too much screen time"]
  A -- No --> B["Any trio avg ≥ 8h?"]
  B -- Yes --> T
  B -- No --> C["Weekly avg ≥ 6h?"]
  C -- Yes --> T
  C -- No --> F["Not excessive"]

Implementation

function tooMuchScreenTime(hours) {
  let totalHours = 0
  for (let i = 0; i < hours.length; i++) {
    // Check if any day has 10 or more hours
    if (hours[i] >= 10) {
      return true
    }

    totalHours += hours[i]

    // Check averages of three consecutive days
    if (i >= 2) {
      const threeDayAvg = (hours[i] + hours[i - 1] + hours[i - 2]) / 3
      if (threeDayAvg >= 8) {
        return true
      }
    }
  }

  // Calculate weekly average
  const weeklyAvg = totalHours / hours.length
  if (weeklyAvg >= 6) {
    return true
  }

  return false
}

Complexity Analysis

  • Time: O(1)O(1) (array size is fixed)
  • Space: O(1)O(1) (only scalar variables)

Reflections & Learnings

  • Sliding window for moving averages
  • Short-circuiting for efficiency
  • Importance of covering all edge cases

Resources & References

freecodecamp daily-challenge