Iterating over arrays in Go - Step-by-Step Execution

Concept Flow - Iterating over arrays

Start

↓

Initialize index i=0

↓

Check: i < length of array?

No→End

Yes↓

Access array[i

↓

Process element

↓

Increment i (i = i+1)

↩Back to Check

Start with index 0, check if it's less than array length, process element, increment index, repeat until done.

Execution Sample

Go

package main

import "fmt"

func main() {
    arr := [3]int{10, 20, 30}
    for i := 0; i < len(arr); i++ {
        fmt.Println(arr[i])
    }
}

This code prints each element of the array one by one.

Execution Table

Iteration	i	Condition (i < len(arr))	Action	Output
1	0	0 < 3 (true)	Print arr[0] = 10	10
2	1	1 < 3 (true)	Print arr[1] = 20	20
3	2	2 < 3 (true)	Print arr[2] = 30	30
4	3	3 < 3 (false)	Exit loop

💡 i reaches 3, condition 3 < 3 is false, loop ends

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
i	0	1	2	3	3
arr[i]	arr[0]=10	arr[1]=20	arr[2]=30	-	-

Key Moments - 3 Insights

Why does the loop stop when i equals the length of the array?

Because the condition i < len(arr) becomes false at that point, as shown in execution_table row 4, so the loop exits.

Why do we start the index i at 0 instead of 1?

Array indexes in Go start at 0, so the first element is at arr[0], as seen in execution_table row 1.

What happens if we try to access arr[i] when i equals the array length?

It causes an error because arr[len(arr)] is out of bounds; the loop condition prevents this by stopping before i reaches len(arr).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of i during the third iteration?

A 2

B 3

C 1

D 0

💡 Hint

Check the 'i' column in execution_table row 3.

At which iteration does the loop condition become false?

A Iteration 2

B Iteration 3

C Iteration 4

D Iteration 1

💡 Hint

Look at the 'Condition' column in execution_table row 4.

If the array had 5 elements instead of 3, how many times would the loop run?

A 3 times

B 5 times

C 4 times

D 6 times

💡 Hint

The loop runs once for each index from 0 up to length-1, so equal to array length.

Concept Snapshot

Go arrays start at index 0.
Use for loop: for i := 0; i < len(arr); i++ {}
Access elements with arr[i].
Loop runs while i < length.
Stops before i equals length to avoid errors.

Full Transcript

This visual trace shows how to iterate over arrays in Go. We start with index i at 0, check if i is less than the array length, then access and print arr[i]. After processing, we increment i by 1 and repeat. The loop stops when i equals the array length, preventing out-of-bounds errors. The variable tracker shows i increasing from 0 to 3, and the output prints each array element in order.