Insertion Sort

Build the sorted prefix one item at a time, shifting larger values right until the current key can be inserted.

Algorithm

The checked-in replay follows the same small input and final output across all 21 DSA books, so this Go DSA implementation can be compared directly with the other languages.

Basic Implementation

basic.go

package main

import "fmt"

func main() {
	arr := []int{5, 1, 4, 2, 8}
	for i := 1; i < len(arr); i++ {
		key := arr[i]
		j := i - 1
		for j >= 0 && arr[j] > key {
			arr[j+1] = arr[j]
			j--
		}
		arr[j+1] = key
	}
	fmt.Println(arr)
}

Complexity

Time: O(n^2) worst and average, O(n) best
Space: O(1)
Stable: yes

Implementation notes

Keep the explicit algorithmic steps instead of calling a standard-library sort. The replay is meant to expose comparisons, movement, and recursion.
The implementation is intentionally compact for learning and replay, not a production sorting utility.

sorted prefix Positions before the scan index are already sorted.

shifting Larger values move one slot right to make room for the key.