基础算法（二）：堆排序，快速排序

基本的算法

堆排序，快速排序

堆排序：

package alg;

import java.util.Arrays;

/**
 * @author zha
 * 算法的复杂度为O(nlogn)
 */
public class HeapSort {

    public static void main(String[] args) {
        int[] array = { 5, 2, 4, 6, 1, 3, 23, 434, 55, 6, 788, 89, 0 };
        heapSort(array, 0 , array.length- 1);
        System.out.println(Arrays.toString(array));

    }

    private static void heapSort(int[] array, int from, int to) {
        buildHeap(array,from,to);
        int length = to - from +1;
        swap(array,from,to);
        while(length > 1){
            for (int i = to - 1; i >= from; i--) {
                buildHeap(array, from, i);
                swap(array, i, from);
            }
            length--;
        }
        
    }

    private static void buildHeap(int[] array, int from, int to) {
        int length = to - from +1;
        int mid = from + (length >> 1);
        for (int i = mid ; i >= 0 ;i--) {
            MAXHeap(array,from ,to, i);
        }
    }

    private static void MAXHeap(int[] array, int from, int to, int index) {
        int left = left(index);
        int right = right(index);
        int lagest = 0;
        if(left <= to && array[left] > array[index]){
            lagest = left;
        }else{
            lagest = index;
        }
        
        if(right <= to && array[right] > array[lagest]){
            lagest = right;
        }
        
        if(lagest != index){
            swap(array,index,lagest);
            MAXHeap(array, from,to,lagest);
        }
    }

    private static void swap(int[] array, int i, int j) {
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
        
    }

    private static int left(int i){
        return 2*(i+1)-1;
    }
    
    private static int right(int i){
        return 2*(i+1);
    }
}

快速排序：