CODEWITHSUNDEEP
go
Hunar
Hunar

Reputation: 349

how to sort by indices in golang

I'm having difficulty porting some code from matlab to golang I want to know how can I get array indices after sorting them in golang, and then how can I use these indices to re-arrange another array? for example the matlab code below does that but I can't figure out doing the same thing in Go. Any help is deeply appreciated.

x=[3 4 2 1 6];
y=[11 12 15 16 17];
[sorted_x_vals, sorted_x_indices]=sort(x);
c=y(sorted_x_indices);  // re-arrange y according to the sorted indices

// c= 16 15 11 12 17

Thanks a lot in advance

Upvotes: 3

Views: 1543

Answers (1)

Mr_Pink
Mr_Pink

Reputation: 109404

You can crate a sort.Interface implementation to sort the slices in unison, based on the first slice's values:

https://play.golang.org/p/y0EFj8wUN0

type by struct {
    Indices []int
    Values  []int
}

func (b by) Len() int           { return len(b.Values) }
func (b by) Less(i, j int) bool { return b.Indices[i] < b.Indices[j] }
func (b by) Swap(i, j int) {
    b.Indices[i], b.Indices[j] = b.Indices[j], b.Indices[i]
    b.Values[i], b.Values[j] = b.Values[j], b.Values[i]
}

func main() {
    x := []int{3, 4, 2, 1, 6}
    y := []int{11, 12, 15, 16, 17}

    sort.Sort(by{Indices: x, Values: y})
    fmt.Println(x)
    fmt.Println(y)
}

// [1 2 3 4 6]
// [16 15 11 12 17]

Or if you wanted to sort any number of slices like this you could define a [][]int type like so

type matrix [][]int
func (m matrix) Len() int {return len(m[0])}
func (m matrix) Less(i, j int) bool { return m[0][i] < m[0][j] }
func (m matrix) Swap(i, j int) {
    for _, s := range m {
        s[i], s[j] = s[j], s[i]
    }
}

func main() {
    x := []int{3, 4, 2, 1, 6}
    y := []int{11, 12, 15, 16, 17}
    z := []int{22, 33, 44, 55, 66}

    sort.Sort(matrix{x, y, z})
    fmt.Println(x)
    fmt.Println(y)
    fmt.Println(z)
}
// [1 2 3 4 6]
// [16 15 11 12 17]
// [55 44 22 33 66]

Upvotes: 4

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