Quicksort实现中的错误（无限循环）

Question

我试图实施quicksort。我写的程序适用于某些列表，但在某些列表中，我似乎在三个while循环之间得到了无限循环。 ＆＃34;在三个while循环之间＆＃34;意思是它的意思;它是内在的一个，有时是它;它是外层的一个。我哪里弄错了？感谢

def quick_sort_over(array):
print "Original array: ", array
quick_sort(array, 0, len(array) - 1)

def quick_sort(array, start, end):
    if start >= end:
        return 
    else:
        partition_point = partition(array, start, end)
        quick_sort(array, start, partition_point - 1)
        if partition_point != end:
            quick_sort(array, partition_point + 1, end)

def partition(array, start, end):
    print "|start: ", start, "||end: ", end
    part_val = array[start]
    left_ptr = start + 1
    right_ptr = end

    while right_ptr > left_ptr:
        while right_ptr > left_ptr and array[left_ptr] < part_val:
            print "left ptr: ", left_ptr, "right ptr: ", right_ptr
            left_ptr += 1
        while right_ptr > left_ptr and array[right_ptr] > part_val:
           print "left ptr: ", left_ptr, "right ptr: ", right_ptr
           right_ptr -= 1

        temp = array[left_ptr]
        array[left_ptr] = array[right_ptr]
        array[right_ptr] = temp

    if array[start] > array[left_ptr]:
        temp = array[start]
        array[start] = array[left_ptr]
        array[left_ptr] = temp

    if left_ptr == start + 1:
        left_ptr = start
    print "array has been altered to: ", array
    print "returning: ", left_ptr
    return left_ptr

array = [9, 1, 8, 2, 7, 3, 6, 4, 6, 5, 34, 4, 56, 4, 3]
quick_sort_over(array)
print array