Java实现堆排序

Posted 2020-09-10 卡洛小豆

输入一个数m表示要排序的数的多少，随机生成m个0~10000之间的数进行堆排序。

import java.util.Random;
import java.util.Scanner;

import org.junit.Test;

public class Heap_Sort {

    public static void makeHeap(int A[], int n) {

        A[n] = A[0];
        for (int i = n / 2; i >= 1; i--) {
            shift_down(A, n, i);
        }
    }

    private static void shift_down(int A[], int n, int i) {

        boolean done = true;
        while (done && i * 2 <= n) {
            i = i * 2;
            if ((i + 1) <= n && A[i + 1] > A[i])
                i++;
            if (A[i / 2] < A[i])
                swap(A, i / 2, i);
        }

    }

    private static void swap(int a[], int x, int y) {

        int t;
        t = a[x];
        a[x] = a[y];
        a[y] = t;
    }

    public static void sortHeap(int A[], int n) {

        makeHeap(A, n);

        swap(A, n, 1);

        for (int i = n - 1; i > 1; i--) {
            shift_down(A, i, 1);
            swap(A, i, 1);
        }

    }

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int A[] = new int[n + 1];
        Random r = new Random();

        for (int i = 0; i < n; i++) {
            A[i] = r.nextInt(10000);
        }
        sortHeap(A, n);
        for (int i = 1; i <= n; i++) {
            System.out.print(A[i] + "\t");
        }
    }
}