Algorithm design (planning solutions) in Intro to Computing - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the algorithm by defining the first step.

Intro to Computing

step1 = "[1]"

Drag options to blanks, or click blank then click option'

ARun the program

BWrite the code

CIdentify the problem

DTest the output

Attempts:

3 left

💡 Hint

Common Mistakes

Starting with writing code before understanding the problem

Trying to test output without a plan

The first step in algorithm design is to identify the problem clearly before planning a solution.

2fill in blank

medium

Complete the code to represent the step where you plan the solution.

Intro to Computing

step2 = "[1]"

Drag options to blanks, or click blank then click option'

ADesign the algorithm

BRun the program

CDebug the code

DIdentify the problem

Attempts:

3 left

💡 Hint

Common Mistakes

Skipping the design and jumping to coding

Confusing debugging with planning

After identifying the problem, the next step is to design the algorithm, which means planning the steps to solve the problem.

3fill in blank

hard

Fix the error in the code to correctly represent the step where you check the algorithm.

Intro to Computing

step3 = "[1]"

Drag options to blanks, or click blank then click option'

ATest the algorithm

BWrite the code

CIdentify the problem

DIgnore errors

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing testing with writing code

Ignoring errors during planning

Testing the algorithm means checking if the planned steps work correctly before coding.

4fill in blank

hard

Fill both blanks to complete the algorithm design steps in order.

Intro to Computing

steps = ["[1]", "[2]"]

Drag options to blanks, or click blank then click option'

AIdentify the problem

BWrite the code

CDesign the algorithm

DTest the algorithm

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing the order of steps

Starting with coding before planning

The correct order starts with identifying the problem, then designing the algorithm as the plan.

5fill in blank

hard

Fill all three blanks to complete the main steps of algorithm design.

Intro to Computing

algorithm_steps = ["[1]", "[2]", "[3]"]

Drag options to blanks, or click blank then click option'

AIdentify the problem

BDesign the algorithm

CTest the algorithm

DRun the program

Attempts:

3 left

💡 Hint

Common Mistakes

Skipping testing

Running the program before testing the algorithm

The main steps are: identify the problem, design the algorithm, then test the algorithm before running code.

Practice

1. What is the main purpose of designing an algorithm before coding?

easy

A. To plan clear steps to solve a problem

B. To write the final program code

C. To test the program output

D. To choose the programming language

Solution

1. Step 1: Understand the role of an algorithm

   An algorithm is a step-by-step plan to solve a problem before coding.

2. Step 2: Differentiate algorithm from coding and testing

   Coding is writing the program, testing checks output, but algorithm is planning steps.

3. Final Answer:

   To plan clear steps to solve a problem -> Option A

4. Quick Check:

   Algorithm = plan steps [OK]

Hint: Algorithms are plans, not code or tests [OK]

Common Mistakes:

• Confusing algorithm with coding
• Thinking algorithm is testing output
• Believing algorithm chooses language

2. Which of the following is the correct way to start an algorithm for finding the largest number in a list?

easy

A. Set largest to 0

B. Set largest to the first number in the list

C. Print the list

D. Sort the list alphabetically

Solution

1. Step 1: Understand initialization in algorithms

   To find the largest number, start by assuming the first number is the largest.

2. Step 2: Evaluate other options

   Setting largest to 0 may fail if all numbers are negative; printing or sorting alphabetically is unrelated.

3. Final Answer:

   Set largest to the first number in the list -> Option B

4. Quick Check:

   Initialize largest with first list item [OK]

Hint: Initialize with first list item, not zero [OK]

Common Mistakes:

• Starting largest at 0 without checking list values
• Sorting list alphabetically instead of numerically
• Printing list instead of initializing variable

3. Consider this algorithm to sum numbers from 1 to 4:

sum = 0
for i in range(1, 5):
  sum = sum + i
print(sum)

What will be the output?

medium

A. 10

B. 15

C. 0

D. Error

Solution

1. Step 1: Understand the loop range

   The loop runs with i = 1, 2, 3, 4 (range(1,5) excludes 5).

2. Step 2: Calculate sum step-by-step

   sum = 0+1=1, 1+2=3, 3+3=6, 6+4=10.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   1+2+3+4 = 10 [OK]

Hint: Sum numbers 1 to 4 = 10 quickly [OK]

Common Mistakes:

• Including 5 in the sum
• Confusing range end as inclusive
• Forgetting to add all numbers

4. This algorithm is meant to find the smallest number in a list:

numbers = [3, 1, 4]
smallest = 0
for num in numbers:
  if num < smallest:
    smallest = num
print(smallest)

What is the error in this algorithm?

medium

A. The print statement is missing parentheses

B. The loop should use 'while' instead of 'for'

C. The comparison should be 'num > smallest'

D. smallest should start as the first list number, not 0

Solution

1. Step 1: Check initialization of smallest

   Starting smallest at 0 fails if all numbers are positive and greater than 0.

2. Step 2: Correct initialization

   Set smallest to the first number in the list (3) to compare properly.

3. Final Answer:

   smallest should start as the first list number, not 0 -> Option D

4. Quick Check:

   Initialize smallest with first list item [OK]

Hint: Initialize smallest with first list item, not zero [OK]

Common Mistakes:

• Using wrong comparison operator
• Confusing for and while loops
• Ignoring initialization importance

5. You want to design an algorithm to count how many words in a sentence start with the letter 'a'. Which step should you include in your algorithm?

hard

A. Sort the words alphabetically before counting

B. Count all letters 'a' in the sentence regardless of position

C. Split the sentence into words and check each word's first letter

D. Replace all 'a's with 'b's before counting

Solution

1. Step 1: Break sentence into words

   Splitting the sentence into words allows checking each word individually.

2. Step 2: Check first letter of each word

   Count only words whose first letter is 'a' to meet the problem requirement.

3. Final Answer:

   Split the sentence into words and check each word's first letter -> Option C

4. Quick Check:

   Check first letter of each word [OK]

Hint: Split sentence, check first letter of each word [OK]

Common Mistakes:

• Counting all 'a's, not just word starts
• Sorting words unnecessarily
• Replacing letters before counting