java算法----排序----（7）堆排序

package log;

import java.util.Arrays;

public class Test4 {
    /**
     * 堆排序
     * 
     * @param args
     */
    public static void main(String[] args) {
        int arr[] = { 49, 20, 36, 51, 18, 94, 61, 31, 50 };

        // 循环输出该数组内容
        System.out.println("排序之前：");
        for (int a : arr) {
            System.out.print(a + "\t");
        }
        System.out.println();

        int arrlength = arr.length;

        // 循环建堆
        for (int i = 0; i < arrlength - 1; i++) {
            build(arr, arrlength - 1 - i);
            swap(arr, 0, arrlength - 1 - i);
            System.out.println(Arrays.toString(arr));
        }

        // 循环输出该数组内容
        System.out.println("排序之后：");
        for (int a : arr) {
            System.out.print(a + "\t");
        }
        System.out.println();

    }

    private static void build(int[] data, int lastIndex) {
        for (int i = (lastIndex - 1) / 2; i >= 0; i--) {
            int k = i;
            while (k * 2 + 1 <= lastIndex) {
                int bigIndex = 2 * k + 1;
                if (bigIndex < lastIndex) {
                    if (data[bigIndex] < data[bigIndex + 1]) {
                        bigIndex++;
                    }
                }

                if (data[k] < data[bigIndex]) {
                    swap(data, k, bigIndex);
                    k = bigIndex;
                } else {
                    break;
                }

            }
        }
    }

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

}

 

下面是控制台的输出