排序(六)-堆排序

来源：互联网发布：数据分析助理前景如何编辑：程序博客网时间：2024/04/28 03:29

稳定性:unstable sort

空间:In-place sort

最优复杂度:O(nlgn)

最差复杂度:O(nlgn)

伪代码:

Max_Heapify(A,i){    heapsize = heapsize[A];    largest = i;    if left(i) <= heapsize && A[largest] < A[left(i)]        largest = left(i);    else if right(i) <= heapsize && A[largest] < A[right(i)]        largest = right(i);    if(largest != i)        swap A[i] <-> A[largest];        Max_Heapify(A,largest);}build_max_heap(A){    for i=floor(n/2) to 1        Max_Heapify(A,i);}heapsort(A){    build_max_heap(A);    for i=n to 2        swap A[1] <->A[heapsize]        heapsize--;        Max_Heapify(A,1);}

Java代码:

import java.util.Arrays;public class Main {int heapsize;public static void main(String[] args){Main m = new Main();int[] A = {0,1,2,3,5,4,7,9,1,2,5,3,2,1};m.heapSort(A);System.out.println(Arrays.toString(A));//输出:[1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 5, 7, 9]}public void maxHeapify(int[] A,int i){int largest = i;if(left(i) <= heapsize && A[largest] < A[left(i)])largest = left(i);if(right(i) <= heapsize && A[largest] < A[right(i)])largest = right(i);if(largest != i){swap(A,i,largest);maxHeapify(A,largest);}}public void buildMaxHeap(int[] A){heapsize = A.length - 1;for(int i = (A.length-1)/2; i > 0; --i){maxHeapify(A,i);}}public void heapSort(int[] A){buildMaxHeap(A);for(int i = (A.length-1); i > 1; --i){swap(A,1,heapsize);heapsize--;maxHeapify(A,1);}}public int left(int i){return 2 * i;}public int right(int i){return 2 * i + 1;}public void swap(int[] A,int x,int y){int temp = A[x];A[x] = A[y];A[y] = temp;}}

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