如何在Go中嵌入和覆盖结构

Question

I am constructing the min/max heaps of ints to satisfy the interface from container/heap.

The min heap works well such as

type MinHeapInt []int

func (h MinHeapInt) Len() int {
    return len(h)
}

func (h MinHeapInt) Less(i, j int) bool {
    return h[i] < h[j]
}

func (h MinHeapInt) Swap(i, j int) {
    h[i], h[j] = h[j], h[i]
}

func (h *MinHeapInt) Peek() interface{} {
    return (*h)[0]
}

func (h *MinHeapInt) Push(x interface{}) {
    *h = append(*h, x.(int))
}

func (h *MinHeapInt) Pop() interface{} {
    length := len(*h)
    res := (*h)[length - 1]
    *h = (*h)[0 : length - 1]
    return res
}

Now I am trying to develop the max heap by only overriding the Less method.

The first solution does not work since it cannot find the array

type MaxHeapInt struct {
    MinHeapInt
}

func (h MaxHeapInt) Less(i, j int) bool {
    return h[i] > h[j]
}

The second solution only keeps the Less method.

type MaxHeapInt MinHeapInt

func (h MaxHeapInt) Less(i, j int) bool {
    return h[i] > h[j]
}

Wonder if there is anyway to get around. Thanks!

Answer 1

Your first solution is trying to index the MaxHeapInt struct, not the MinHeapInt slice.

type MaxHeapInt struct {
    MinHeapInt
}

func (h MaxHeapInt) Less(i, j int) bool {
    return h.MinHeapInt[i] > h.MinHeapInt[j]
}

If you want them to be initialized the same, then create a partial heap implementation, and wrap in the desired struct (similar to the wrapper example in the sort package).

type Max struct{ IntHeap }

func (h Max) Less(i, j int) bool {
    return h.IntHeap[i] > h.IntHeap[j]
}

type Min struct{ IntHeap }

func (h Min) Less(i, j int) bool {
    return h.IntHeap[i] < h.IntHeap[j]
}

type IntHeap []int

func (h IntHeap) Len() int { return len(h) }

func (h IntHeap) Swap(i, j int) { h[i], h[j] = h[j], h[i] }

func (h *IntHeap) Peek() interface{} { return (*h)[0] }

func (h *IntHeap) Push(x interface{}) {
    *h = append(*h, x.(int))
}

func (h *IntHeap) Pop() interface{} {
    length := len(*h)
    res := (*h)[length-1]
    *h = (*h)[0 : length-1]
    return res
}

// Now these can be initialized like
//     Min{IntHeap{1, 2, 3}}
//     Max{IntHeap{1, 2, 3}}