堆排序(heapsort)
堆排序(heapsort)
Heap Sort
- Complete Binary Tree
- parent > children
heapify
n = i ---> parent = (i - 1) / 2
----> c1 = 2i + 1
----> c2 = 2i + 2
#include <stdio.h>
void swap(int arr[], int i, int j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
void heapify(int tree[], int n, int i) {
if (i >= n) {
return ;
}
int c1 = 2 * i + 1;
int c2 = 2 * i + 2;
int max = i;
if (c1 < n && tree[c1] > tree[max]) {
max = c1;
}
if (c2 < n && tree[c2] > tree[max]) {
max = c2;
}
if (max != i) {
swap(tree, max, i);
heapify(tree, n, max);
}
}
void build_heap(int tree[], int n) {
int last_node = n - 1;
int parent = (last_node - 1) / 2;
int i;
for (i = parent; i >= 0; i--) {
heapify(tree, n, i);
}
}
void heap_sort(int tree[], int n) {
build_heap(tree, n);
int i;
for (i = n - 1; i >= 0; i--) {
swap(tree, i, 0);
heapify(tree, i, 0);
}
}
int main()
{
int tree[] = {2, 5, 3, 1, 10, 4};
int n = 6;
heap_sort(tree, n);
int i;
for (i = 0; i < n; i++) {
printf("%d\n",tree[i]);
}
return 0;
}
/* !< output */
1
2
3
4
5
10