Why Arrays Exist and What Problem They Solve in DSA Go - See It Work

Why Arrays Exist and What Problem They Solve

📖 Scenario: Imagine you run a small bakery. Every day, you bake a fixed number of bread loaves and want to keep track of their prices. You need a simple way to store and access these prices quickly and in order.

🎯 Goal: You will create an array to store the prices of 5 bread loaves. Then, you will set a price threshold and find which loaves cost more than that threshold. Finally, you will print the prices of those loaves.

📋 What You'll Learn

Create an array called prices with exactly 5 float64 values: 2.5, 3.0, 1.75, 4.0, 2.25

Create a variable called threshold with the value 2.5

Use a for loop with index i to check each price in prices

Inside the loop, use an if statement to find prices greater than threshold

Print each price greater than threshold on its own line

💡 Why This Matters

🌍 Real World

Arrays help store lists of items like prices, temperatures, or scores in many real-world apps.

💼 Career

Understanding arrays is key for programming jobs that handle collections of data efficiently.

1

Create the array of bread prices

Create an array called prices with these exact 5 float64 values: 2.5, 3.0, 1.75, 4.0, 2.25

DSA Go

# Your code here

Hint

Use prices := [5]float64{...} to create the array with the exact values.

2

Set the price threshold

Create a variable called threshold and set it to 2.5

DSA Go

package main

func main() {
    prices := [5]float64{2.5, 3.0, 1.75, 4.0, 2.25}
    // Your code here
}

Hint

Use threshold := 2.5 to create the variable.

3

Find prices greater than the threshold

Use a for loop with index i to check each price in prices. Inside the loop, use an if statement to find prices greater than threshold.

DSA Go

package main

func main() {
    prices := [5]float64{2.5, 3.0, 1.75, 4.0, 2.25}
    threshold := 2.5
    // Your code here
}

Hint

Use for i := 0; i < len(prices); i++ to loop and if prices[i] > threshold to check.

4

Print the prices above the threshold

Run the program to print each price in prices that is greater than threshold. Each price should appear on its own line.

DSA Go

package main

import "fmt"

func main() {
    prices := [5]float64{2.5, 3.0, 1.75, 4.0, 2.25}
    threshold := 2.5
    for i := 0; i  threshold {
            fmt.Println(prices[i])
        }
    }
    // Your code here
}

Hint

The program should print 3 and 4 each on its own line.

Practice

1. Why do arrays exist in programming languages like Go?

easy

A. To perform mathematical calculations faster

B. To store values of different types in a single variable

C. To store multiple values of the same type in a fixed-size sequence

D. To replace all other data structures

Solution

1. Step 1: Understand the purpose of arrays

   Arrays are designed to hold multiple values of the same type together in a fixed-size sequence.

2. Step 2: Compare with other options

   The other options describe features not specific to arrays or are incorrect.

3. Final Answer:

   To store multiple values of the same type in a fixed-size sequence -> Option C

4. Quick Check:

   Arrays = fixed-size same-type storage [OK]

Hint: Arrays hold same-type items in order with fixed size [OK]

Common Mistakes:

• Thinking arrays can store different types together
• Confusing arrays with lists or slices
• Believing arrays perform calculations themselves

2. Which of the following is the correct way to declare an array of 5 integers in Go?

easy

A. var arr [5]int

B. int arr[5]

C. var arr []int = make(5)

D. arr := []int{5}

Solution

1. Step 1: Recall Go array declaration syntax

   In Go, arrays are declared with fixed size: var arr [5]int declares an array of 5 integers.

2. Step 2: Analyze other options

   int arr[5] is invalid C-style syntax in Go. var arr []int = make(5) uses make incorrectly (make is for slices, not arrays). arr := []int{5} declares a slice, not an array.

3. Final Answer:

   var arr [5]int -> Option A

4. Quick Check:

   Array declaration = var arr [size]type [OK]

Hint: Use var name [size]type for arrays in Go [OK]

Common Mistakes:

• Using make() for arrays instead of slices
• Confusing slices with arrays
• Initializing arrays with fewer elements than size without explicit zeros

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

package main
import "fmt"
func main() {
  var arr [3]int
  arr[0] = 10
  arr[1] = 20
  arr[2] = 30
  fmt.Println(arr)
}

medium

A. [10 20]

B. [10 20 30]

C. [0 0 0]

D. Compilation error

Solution

1. Step 1: Understand array initialization and assignment

   The array of size 3 is declared with default zeros. Then each index is assigned 10, 20, and 30 respectively.

2. Step 2: Print the array

   Printing the array shows all elements in order: [10 20 30].

3. Final Answer:

   [10 20 30] -> Option B

4. Quick Check:

   Array after assignments = [10 20 30] [OK]

Hint: Arrays print all elements in order inside brackets [OK]

Common Mistakes:

• Expecting commas between elements in output
• Thinking unassigned elements remain uninitialized
• Confusing slices and arrays output format

4. Identify the error in this Go code snippet that tries to assign a value to an array element:

package main
func main() {
  var arr [3]int
  arr[3] = 100
}

medium

A. Index out of range error at runtime

B. Compilation error: index 3 out of bounds

C. No error, code runs fine

D. Array size is not declared

Solution

1. Step 1: Check array size and index used

   The array has size 3, so valid indices are 0, 1, and 2. Index 3 is out of bounds.

2. Step 2: Understand Go's bounds checking

   Go performs bounds checking at runtime and panics with an index out of range error on out-of-bounds access.

3. Final Answer:

   Index out of range error at runtime -> Option A

4. Quick Check:

   Array index must be less than size [OK]

Hint: Array indices go from 0 to size-1 only [OK]

Common Mistakes:

• Using index equal to array size
• Expecting runtime error instead of compile error
• Confusing slices with arrays for index bounds

5. You want to store the daily temperatures for a week using an array in Go. Which of the following is the best approach and why?

medium

A. Use a single float64 variable and update it daily

B. Use a slice without fixed size to store temperatures

C. Use a map with string keys for days and float64 values

D. Use an array of size 7 with type float64 to store temperatures

Solution

1. Step 1: Analyze the problem requirements

   We need to store exactly 7 temperature values, one for each day of the week.

2. Step 2: Choose the best data structure

   An array of size 7 with float64 type fits perfectly because the size is fixed and known. Slices or maps add unnecessary overhead here. A single variable cannot hold multiple values.

3. Final Answer:

   Use an array of size 7 with type float64 to store temperatures -> Option D

4. Quick Check:

   Fixed-size data = array best choice [OK]

Hint: Fixed known size? Use array for efficient storage [OK]

Common Mistakes:

• Choosing slices when size is fixed and known
• Using maps when order matters and keys are unnecessary
• Trying to store multiple values in one variable