Initial data commit

Task/Sorting-algorithms-Heapsort/Go/sorting-algorithms-heapsort-1.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+  "sort"
+  "container/heap"
+  "fmt"
+)
+
+type HeapHelper struct {
+    container sort.Interface
+    length    int
+}
+
+func (self HeapHelper) Len() int { return self.length }
+// We want a max-heap, hence reverse the comparison
+func (self HeapHelper) Less(i, j int) bool { return self.container.Less(j, i) }
+func (self HeapHelper) Swap(i, j int) { self.container.Swap(i, j) }
+// this should not be called
+func (self *HeapHelper) Push(x interface{}) { panic("impossible") }
+func (self *HeapHelper) Pop() interface{} {
+    self.length--
+    return nil // return value not used
+}
+
+func heapSort(a sort.Interface) {
+    helper := HeapHelper{ a, a.Len() }
+    heap.Init(&helper)
+    for helper.length > 0 {
+        heap.Pop(&helper)
+    }
+}
+
+func main() {
+    a := []int{170, 45, 75, -90, -802, 24, 2, 66}
+    fmt.Println("before:", a)
+    heapSort(sort.IntSlice(a))
+    fmt.Println("after: ", a)
+}

Task/Sorting-algorithms-Heapsort/Go/sorting-algorithms-heapsort-2.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+  "sort"
+  "fmt"
+)
+
+func main() {
+    a := []int{170, 45, 75, -90, -802, 24, 2, 66}
+    fmt.Println("before:", a)
+    heapSort(sort.IntSlice(a))
+    fmt.Println("after: ", a)
+}
+
+func heapSort(a sort.Interface) {
+    for start := (a.Len() - 2) / 2; start >= 0; start-- {
+        siftDown(a, start, a.Len()-1)
+    }
+    for end := a.Len() - 1; end > 0; end-- {
+        a.Swap(0, end)
+        siftDown(a, 0, end-1)
+    }
+}
+
+
+func siftDown(a sort.Interface, start, end int) {
+    for root := start; root*2+1 <= end; {
+        child := root*2 + 1
+        if child+1 <= end && a.Less(child, child+1) {
+            child++
+        }
+        if !a.Less(root, child) {
+            return
+        }
+        a.Swap(root, child)
+        root = child
+    }
+}