Learn the python path---python small algorithm Summary (iv)

Title: Merge sort Python implementation

External sort--merging sort principle

Merge sorting basically merges and sorts two sorted data, and if the data you read is not sorted, you can use other sort methods to process the two data before merging the two sorted data.

Importrandom

Importcopy

Number1 =random.sample (range (100), 10)

Number2 =random.sample (range (100), 10)

Number1.sort ()

Number2.sort ()

Defrecursive_sort (Lista, LISTB):

"""

Recursive implementation

"""

Iflen (lista) = = 0:

return LISTB

Elif len (listb) = = 0:

return lista

Elif Lista[0] < Listb[0]:

return [lista[0]] +recursive_sort (lista[1:], Listb)

Else

return [listb[0]] +recursive_sort (listb[1:], Lista)

Defsort (Lista, LISTB):

"""

Non-recursive implementation

"""

len_a = Len (lista)

Len_b = Len (LISTB)

If len_a = 0:

return LISTB

elif Len_b = = 0:

return lista

Else

i = 0

j = 0

LISTC = []

While I < len_a and J < len_b:

If Lista[i] <= Listb[j]:

Listc.append (Lista[i])

i + 1

Else

Listc.append (Listb[j])

J + 1

While I < len_a:

Listc.append (Lista[i])

i + 1

While J < len_b:

Listc.append (Listb[j])

J + 1

Return LISTC

Printnumber1

Printnumber2

LISTC =recursive_sort (Number1, number2)

Printlistc

LISTC =sort (Number1, number2)

The results of the operation are as follows:

[9, 15, 20, 27, 32, 33, 56, 62, 78, 84]

[29, 35, 46, 50, 66, 69, 84, 87, 89, 90]

[9, 15, 20, 27, 29, 32, 33, 35, 46, 50, 56, 62, 66, 69, 78, 84, 84, 87, 89, 90]

Topic: Traversal string

TheString = ' Ix lixkxex xpxytxhxonx! '
Defprintengine (c):
IFC!= ' x ':
PRINTC,
Map (printengine,thestring)

Output result: I l i k e p y t h o n!

Topic: Division Tips

A python divides two integers, and the default result is an integer. Using the following statement, you can get the result of dividing as a decimal

From __future__ Import Division
Print7/3
Output results:

2.3333333333

Title: Print string Format

print ' | ', ' * ' Ljust (10), ' | '

print ' | ', ' * ' Ljust (10, '-'), ' | '

print ' | ', ' * ' Rjust (10, '-'), ' | '

print ' | ', ' * '. Center (10, '-'), ' | '

For a in range (1, 6):

print ' A = '. Ljust (5), repr (a). Ljust (a), ' B = '. Ljust (5), repr (A * 2)

| * |
|*--------- |
|---------* |
|----*----- |
A= 1 B = 2
A= 2 B = 4
A= 3 B = 6
A= 4 B = 8
A= 5 B = 10

Initializing multidimensional Arrays

In Python, initializing a 5x3 array of 0 is a good way to

multilist = [[0 for Col in range (5)] Forrow in range (3)]

Multilist[0][0]= ' Love '

Print Multilist

[[' Love ', 0, 0, 0, 0], [0, 0, 0, 0,0], [0, 0, 0, 0, 0]]