排序多维数组/切片

Question

I have created a multidimensional array (slice) in Go as follows:

var distancematrix [5][5]int

So it is a 5*5 array/slice. Now I am inserting values into this slice such that at a point:

distancematrix :  [[0 154 12 35 138] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0]]

Now, I want to sort this array in ascending order, e.g.:

sorteddistancematrix :  [[0 12 35  138 154] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0] [0 0 0 0 0]]

I tried sort.Ints(distancematrix[0]) but it throws an error saying:

cannot use distancematrix[0] (type [5]int) as type []int in argument to sort.Ints

Basically, I want to fetch the smallest non-zero value in the array. How can I sort this array to achieve this?

Answer 1

To get the smallest non-zero element, you don't need to sort it. Sorting an array or slice is relatively a costly operation - compared to just getting the smallest non-zero element.

Generally to get the smallest non-zero element, just loop over the values, and look for the value that fits you best. If you find a better one (in your example a smaller non-zero), keep that and continue.

Example implementation:

func smallestNonZero(s []int) (n int) {
    for _, v := range s {
        if v != 0 && (v < n || n == 0) {
            n = v
        }
    }
    return
}

Note: This function will return 0 if and only if the passed slice does not contain any non-zero element (that is, it's either full of 0s or it's empty or it's nil). This function also works properly if the slice (also) contains negative numbers.

If you have an array and not a slice, simply slice the array (which results in a slice) and so you can pass it to the function above.

Using it:

fmt.Println(smallestNonZero([]int{5, 3, 1, 4}))
fmt.Println(smallestNonZero([]int{0, 3, 5, 8, 0, 2, 9}))
arr := [5]int{0, 154, 12, 35, 138}
fmt.Println(smallestNonZero(arr[:]))

Output (try it on the Go Playground):

1
2
12