归并排序

归并排序

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//将有二个有序数列a[first...mid]和a[mid...last]合并。   void mergearray(int a[], int first, int mid, int last, int temp[])  {      int i = first, j = mid + 1;      int m = mid,   n = last;      int k = 0;            while (i <= m && j <= n)      {          if (a[i] <= a[j])              temp[k++] = a[i++];          else              temp[k++] = a[j++];      }            while (i <= m)          temp[k++] = a[i++];            while (j <= n)          temp[k++] = a[j++];            for (i = 0; i < k; i++)          a[first + i] = temp[i];  }  void mergesort(int a[], int first, int last, int temp[])  {      if (first < last)      {          int mid = (first + last) / 2;          mergesort(a, first, mid, temp);    //左边有序           mergesort(a, mid + 1, last, temp); //右边有序           mergearray(a, first, mid, last, temp); //再将二个有序数列合并       }  }    bool MergeSort(int a[], int n)  {      int *p = new int[n];      if (p == NULL)          return false;      mergesort(a, 0, n - 1, p);      delete[] p;      return true;  }