此文原创， http://www.cnblogs.com/baokang/p/4735431.html ，禁止转载
GIF 动态图
伪代码
/* From Wikipedia, the free encyclopedia */
1.父子节点特征
iParent = floor((i-1) / 2);
iLeftChild = 2*i + 1;
iRightChild = 2*i + 2;
2.算法伪代码
/* 保持原汁原味就不翻译了 =。= */
procedure heapsort(a, count) is
input: an unordered array a of length count (Build the heap in array a so that largest value is at the root)
heapify(a, count) (The following loop maintains the invariants that a[0:end] is a heap and every element
beyond end is greater than everything before it (so a[end:count] is in sorted order))
end ← count - 1
while end > 0 do
(a[0] is the root and largest value. The swap moves it in front of the sorted elements.)
swap(a[end], a[0])
(the heap size is reduced by one)
end ← end - 1
(the swap ruined the heap property, so restore it)
siftDown(a, 0, end)
(Put elements of 'a' in heap order, in-place)
procedure heapify(a, count) is
(start is assigned the index in 'a' of the last parent node)
(the last element in a 0-based array is at index count-1; find the parent of that element)
start ← floor ((count - 2) / 2) while start ≥ 0 do
(sift down the node at index 'start' to the proper place such that all nodes below
the start index are in heap order)
siftDown(a, start, count - 1)
(go to the next parent node)
start ← start - 1
(after sifting down the root all nodes/elements are in heap order) (Repair the heap whose root element is at index 'start', assuming the heaps rooted at its children are valid)
procedure siftDown(a, start, end) is
root ← start while root * 2 + 1 ≤ end do (While the root has at least one child)
child ← root * 2 + 1 (Left child)
swap ← root (Keeps track of child to swap with) if a[swap] < a[child]
swap ← child
(If there is a right child and that child is greater)
if child+1 ≤ end and a[swap] < a[child+1]
swap ← child + 1
if swap = root
(The root holds the largest element. Since we assume the heaps rooted at the
children are valid, this means that we are done.)
return
else
swap(a[root], a[swap])
root ← swap (repeat to continue sifting down the child now)
Java实现
public void heapsort(int[] a, int count) {
if (count < 2)
return;
heapify(a, count);
int end = count - 1;
while (end > 0) {
swap(a, 0, end);
end--;
siftdown(a, 0, end);
}
}
public void heapify(int[] a, int count) {
int start = (count - 2) / 2;
while (start >= 0) {
siftdown(a, start, count - 1);
start--;
}
}
public void siftdown(int[] a, int start, int end) {
int root = start;
while (root * 2 + 1 <= end) {
int child = root * 2 + 1;
int swap = root;
if (a[swap] < a[child]) {
swap = child;
}
if (child + 1 <= end && a[swap] < a[child + 1]) {
swap = child + 1;
}
if (root == swap) {
return;
} else {
swap(a, root, swap);
}
root = swap;
}
}
public void swap(int[] a, int i, int j) {
int t = a[i];
a[i] = a[j];
a[j] = t;
}