Initial commit

heap.go

@@ -0,0 +1,60 @@
+package coding
+
+import (
+	"maps"
+)
+
+type node struct {
+	symbol byte
+	count  int
+}
+
+type Heap struct {
+	nodes    [256]node
+	bySymbol map[byte]int
+}
+
+func NewHeap() *Heap {
+	h := &Heap{
+		bySymbol: map[byte]int{},
+	}
+
+	for i := 0; i < 256; i++ {
+		h.nodes[i].symbol = byte(i)
+		h.bySymbol[byte(i)] = i
+	}
+
+	return h
+}
+
+func (h Heap) Clone() *Heap {
+	return &Heap{
+		nodes:    h.nodes,
+		bySymbol: maps.Clone(h.bySymbol),
+	}
+}
+
+func (h *Heap) IncrementSymbol(symbol byte) int {
+	nodeIndex := h.bySymbol[symbol]
+	h.nodes[nodeIndex].count++
+
+	iterIndex := nodeIndex
+	for iterIndex != 0 {
+		parentIndex := h.parentIndex(iterIndex)
+
+		if h.nodes[iterIndex].count <= h.nodes[parentIndex].count {
+			break
+		}
+
+		h.nodes[iterIndex], h.nodes[parentIndex] = h.nodes[parentIndex], h.nodes[iterIndex]
+		h.bySymbol[h.nodes[iterIndex].symbol] = iterIndex
+		h.bySymbol[h.nodes[parentIndex].symbol] = parentIndex
+		iterIndex = parentIndex
+	}
+
+	return nodeIndex
+}
+
+func (h Heap) parentIndex(nodeIndex int) int {
+	return (nodeIndex - 1) / 2
+}