Sorting with the sort Package

Go's sort package provides in-place sorting for slices of primitives, a flexible closure-based API for structs, an interface for custom types, and a binary search primitive — all in the standard library.

Sorting primitives

All three functions sort in-place and in ascending order. If you need to preserve the original, copy the slice first.

sort.Slice — sorting structs by any field

The most-used function in the package:

The less function receives indices i and j; return true if element i should come before j.

sort.SliceStable — preserve original order of equal elements

Use SliceStable when equal elements have meaningful relative order (e.g., sort by department then preserve original name order within each department).

Multi-key sort

Chain comparisons in the less function:

sort.Interface — custom types

Implement three methods to make any type sortable with sort.Sort:

Prefer sort.Slice for one-off sorts; implement sort.Interface when the type is always sorted the same way or needs to be passed to functions expecting sort.Interface.

sort.Search — binary search

sort.Search runs binary search in O(log n). The slice must be sorted. The function must be monotone: false for indices before the answer, true from the answer onwards.

sort.Reverse

Checking if sorted