Loop execution flow in Go - Mini Project: Build & Apply

Loop Execution Flow in Go

📖 Scenario: You are helping a small shop owner who wants to count how many items they have in stock. They have a list of item quantities and want to add them up.

🎯 Goal: Build a Go program that uses a for loop to add up all the item quantities and print the total.

📋 What You'll Learn

Create a slice named items with the exact quantities: 3, 7, 2, 9, 4

Create an integer variable named total and set it to 0

Use a for loop with the variable quantity to go through each number in items

Add each quantity to total inside the loop

Print the final value of total

💡 Why This Matters

🌍 Real World

Counting totals is common in shops, inventories, and anywhere you track quantities.

💼 Career

Understanding loop execution flow is essential for processing lists of data in software development.

1

Create the item quantities slice

Create a slice called items with these exact integer values: 3, 7, 2, 9, 4

Go

# Create the items slice with the exact values
# Your code here

Hint

Use items := []int{3, 7, 2, 9, 4} to create the slice.

2

Create the total variable

Create an integer variable called total and set it to 0 inside the main function, below the items slice

Go

package main

func main() {
    items := []int{3, 7, 2, 9, 4}
    // Create total variable and set to 0
    // Your code here
}

Hint

Use total := 0 to create the variable.

3

Add a for loop to sum the items

Use a for loop with the variable quantity to iterate over items and add each quantity to total

Go

package main

func main() {
    items := []int{3, 7, 2, 9, 4}
    total := 0
    // Use a for loop with quantity to add each item to total
    // Your code here
}

Hint

Use for _, quantity := range items and inside the loop add quantity to total.

4

Print the total

Print the value of total using fmt.Println(total). Remember to import the fmt package at the top.

Go

package main

import "fmt"

func main() {
    items := []int{3, 7, 2, 9, 4}
    total := 0
    for _, quantity := range items {
        total += quantity
    }
    // Print the total
    // Your code here
}

Hint

Use fmt.Println(total) to print the total sum.

Practice

1. What is the main purpose of a for loop in Go?

easy

A. To handle errors

B. To define a new variable

C. To repeat a block of code while a condition is true

D. To declare a function

Solution

1. Step 1: Understand the role of loops

   Loops are used to repeat actions multiple times based on a condition.

2. Step 2: Identify the purpose of for in Go

   In Go, the for loop is the only loop and repeats code while a condition holds true.

3. Final Answer:

   To repeat a block of code while a condition is true -> Option C

4. Quick Check:

   Loop = repeat code [OK]

Hint: Loops repeat code while condition true [OK]

Common Mistakes:

• Confusing loops with variable declarations
• Thinking loops handle errors
• Mixing loops with function declarations

2. Which of the following is the correct syntax for a basic for loop in Go that runs 3 times?

easy

A. for i := 0; i < 3; i++

B. for (i = 0; i < 3; i++) { }

C. for i = 0; i < 3; i++ { }

D. for i := 0; i < 3; i++ { }

Solution

1. Step 1: Check Go loop syntax

   Go requires initialization with :=, condition, and post statement inside parentheses without extra parentheses around the whole for.

2. Step 2: Validate each option

   for i := 0; i < 3; i++ { } uses correct syntax: for i := 0; i < 3; i++ { }. Options B and C have wrong parentheses or missing :=. for i := 0; i < 3; i++ misses braces.

3. Final Answer:

   for i := 0; i < 3; i++ { } -> Option D

4. Quick Check:

   Correct Go for loop syntax = for i := 0; i < 3; i++ { } [OK]

Hint: Use := for init, semicolons, braces for loop [OK]

Common Mistakes:

• Using parentheses like C/Java
• Missing := for variable declaration
• Omitting braces {}

3. What will be the output of this Go code?

for i := 1; i <= 3; i++ {
    if i == 2 {
        continue
    }
    fmt.Print(i)
}

medium

A. 13

B. 12

C. 123

D. 23

Solution

1. Step 1: Understand the loop and continue

   The loop runs i from 1 to 3. When i equals 2, continue skips printing.

2. Step 2: Trace output for each i

   i=1 prints '1', i=2 skips print, i=3 prints '3'. Output is '13'.

3. Final Answer:

   13 -> Option A

4. Quick Check:

   Continue skips i=2 print = 13 [OK]

Hint: Continue skips current iteration print [OK]

Common Mistakes:

• Assuming continue prints the skipped value
• Confusing continue with break
• Ignoring loop condition

4. Identify the error in this Go loop code:

for i := 0; i < 5; i++
    fmt.Println(i)

medium

A. Missing braces {} around loop body

B. Incorrect loop condition

C. Variable i not declared

D. Using println instead of Println

Solution

1. Step 1: Check Go loop syntax rules

   Go requires braces {} to define the loop body even if it is one statement.

2. Step 2: Identify missing braces

   The code lacks braces around fmt.Println(i), causing a syntax error.

3. Final Answer:

   Missing braces {} around loop body -> Option A

4. Quick Check:

   Braces required for loop body [OK]

Hint: Always use braces {} for loop body [OK]

Common Mistakes:

• Omitting braces for single statement
• Misreading error as variable issue
• Confusing println with Println

5. Given this Go code, what will be the output?

sum := 0
for i := 1; i <= 5; i++ {
    if i%2 == 0 {
        continue
    }
    if sum > 5 {
        break
    }
    sum += i
}
fmt.Println(sum)

hard

A. 6

B. 9

C. 10

D. 5

Solution

1. Step 1: Trace loop with continue and break

   Loop i=1 to 5, skip even i (2,4). Add odd i to sum until sum > 5, then break.

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

   i=1 (odd): sum=0+1=1
   i=2 (even): continue, skip
   i=3 (odd): sum=1+3=4
   i=4 (even): continue, skip
   i=5 (odd): sum=4+5=9 but before adding, sum=4 which is not >5, so add 5 sum=9. Now sum >5, break after this iteration.

3. Step 3: Check when break occurs

   Break happens after sum=9, but condition checks sum >5 before adding i=5, so sum was 4 before adding 5. Actually, break triggers only if sum >5 before adding i.

4. Step 4: Correct calculation

   At i=5, sum=4 (not >5), so add 5 sum=9. Next iteration would be i=6 (loop ends). So break never triggers because sum >5 check is before adding i.

5. Final Answer:

   9 -> Option B

6. Quick Check:

   Sum after adding odd numbers until break = 9 [OK]

Hint: Check continue and break order carefully [OK]

Common Mistakes:

• Adding after break condition incorrectly
• Ignoring continue skipping even numbers
• Misunderstanding break timing