How to Achieve Case-Insensitive Sorting in Go with sort.Strings()?

Case Insensitive Sorting in Golang with sort.Strings()

In Python, case-insensitive sorting is often achieved using the key parameter of the sorted() function, which allows for custom comparison functions. However, in Go's sort.Strings(), there is no direct equivalent.

To perform case-insensitive sorting in Go, we can leverage Go's powerful slicing capabilities. One approach is to create a custom comparison function that compares the strings' lowercase versions:

<code class="go">sort.Strings(data, func(i, j int) bool {
    return strings.ToLower(data[i]) < strings.ToLower(data[j])
})</code>

This method works well for small data sets, but it can result in excessive string allocations for large inputs.

For more efficient sorting, we can compare the strings rune by rune while ignoring their case:

<code class="go">func lessLower(sa, sb string) bool {
    for {
        rb, nb := utf8.DecodeRuneInString(sb)
        if nb == 0 {
            return false
        }

        ra, na := utf8.DecodeRuneInString(sa)
        if na == 0 {
            return true
        }

        rb = unicode.ToLower(rb)
        ra = unicode.ToLower(ra)

        if ra != rb {
            return ra < rb
        }

        sa = sa[na:]
        sb = sb[nb:]
    }
}

sort.Strings(data, func(i, j int) bool {
    return lessLower(data[i], data[j])
})</code>

This approach avoids unnecessary allocations by directly comparing the runes of the strings.

For further flexibility and language-specific sorting, consider using the collate package, which provides locales and language-specific collation rules.

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