实现合并排序。

class Merge {


  private static Comparable[] compara;
  /**
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  **/


  private static boolean less(Comparable v, Comparable w) {

    return v.compareTo(w) < 0;

  }


  public static boolean isSorted(Comparable[] a) {

    for (int i = 1; i < a.length; i++)

      if (less(a[i], a[i - 1]))

        return false;


    return true;

  }
/**时 代      J a v a   公   众 号 - nowjava.com**/

  private static void merge(Comparable[] a, Comparable[] aux, int lo, int mid, int hi) {

    // copy the array

    for (int k = lo; k <= hi; k++)

      aux[k] = a[k];


    int i = lo, j = mid + 1;


    for (int k = lo; k <= hi; k++) {

      if (i > mid)

        a[k] = aux[j++];

      else if (j > hi)

        a[k] = aux[i++];

      else if (less(aux[j], aux[i]))

        a[k] = aux[j++];

      else

        a[k] = aux[i++];

    }

  }


  private static void sort(Comparable[] a, Comparable[] aux, int lo, int hi) {

    if (hi <= lo)

      return;


    int mid = lo + (hi - lo) / 2; // split the array in 2 parts


    sort(a, aux, lo, mid); // left

    sort(a, aux, mid + 1, hi); // right


    merge(a, aux, lo, mid, hi);

  }


  public static void sort(Comparable[] a) {

    compara = new Comparable[a.length];


    sort(a, compara, 0, a.length - 1);

  }