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：