快速排序Python工作

Question

I have a text file "result.txt". The following code opens result.txt and reads its contents into the list "data". After that, the function "partition" is defined, then the recursive function "quicksort" is defined. Finally, the function quicksort is applied to the list data.

    import io

    with io.open('result.txt', encoding='latin-1') as myfile:
        data = myfile.readlines()

    def partition(list, start, end):
        pivot = list[end]                          # Partition around the last value
        bottom = start-1                           # Start outside the area to be partitioned
        top = end                                  # Ditto

        done = 0
        while not done:                            # Until all elements are partitioned...

            while not done:                        # Until we find an out of place element...
                bottom = bottom+1                  # ... move the bottom up.

                if bottom == top:                  # If we hit the top...
                    done = 1                       # ... we are done.
                    break

                if list[bottom] > pivot:           # Is the bottom out of place?
                    list[top] = list[bottom]       # Then put it at the top...
                    break                          # ... and start searching from the top.

            while not done:                        # Until we find an out of place element...
                top = top-1                        # ... move the top down.

                if top == bottom:                  # If we hit the bottom...
                    done = 1                       # ... we are done.
                    break

                if list[top] < pivot:              # Is the top out of place?
                    list[bottom] = list[top]       # Then put it at the bottom...
                    break                          # ...and start searching from the bottom.

        list[top] = pivot                     

     # Put the pivot in its place.
    return top                                 # Return the split point


def quicksort(list, start, end):
    if start < end:                            # If there are two or more elements...
        split = partition(list, start, end)    # ... partition the sublist...
        quicksort(list, start, split-1)

quicksort(data, 0, (int(len(data))-1))

The quick sort fails to sort the data. Printing data[500500] returns "scheinhei" while printing data[500501] returns "blasende". It is not alphabetically sorted as I want it to be. The data being sorted includes symbols, numbers and letters. How can I get this quick sort to work?

Answer 1

You are almost there, but forgot to sort the second half of the array:

def quicksort(list, start, end):
  if start < end:                            # If there are two or more elements...
    split = partition(list, start, end)    # ... partition the sublist...
    quicksort(list, start, split-1)
    quicksort(list, split+1, end) #we need to sort the second half as well!