I I've finally found how to make a RLE algorithm by watching a tutorial but This tutorial didn' t explain something in that code I didn't get why we write j = i instead of j = 0 (Knowing that I = 0) it's the same no ?
I didn't get why i = j + 1 either. Why i = j + 1 At the end of the function ? Why not simply i += 1 but if we want to repeat a loop in a loop then we do j + 1 ?
Did the first while loop is supposed to repeat the second while loop until the string is finished ?
And finally why encoded_message is repeated two times ? instead of one. We return encoded_message so that's it ? We can simply do print(encode(text)) instead of "print('The encoded message is the output ',encoded_message)" (when we put encode(text) into encoded_message)
I know i'm asking a lot of questions but I just can't memorize the code without understanding it, it would be totally useless and unproductive
def encode(message):
encoded_message = ""
i = 0
while(i<len(message)):
count = 1
ch = message[i]
j = i # ???
while(j<len(message)-1): # GET IT -----------------------------------------------------------
if message[j] == message[j+1]: # if the previous and next characters are the same
count = count + 1 # we increase count variable
j += 1 # we increase j position
# GET IT ----------------------------------------------------------------------------
else:
break
encoded_message = encoded_message + str(count) + ch # "" + count converted to string + character (ch)
i = j + 1 # ???
return encoded_message
text = input('enter your charcter chain...')
encoded_message = encode(text)
print('The encoded message is the output ',encoded_message)
When I replaced j = i by j = 0 nothing is displayed in the terminal
see : no result
There is an outer loop and an inner loop. The outer loop with the variable i starts iterating over the message. The inner loop uses the variable j and starts at the current position of i.
That is: when i=0 then j=0. But when i=5 (for example) then j=5 also.
The inner loops task is to check whether 2 or more identical characters follow one another. If they do i is increased accordingly at the end of the inner loop. So that each letter of the message is only looked at once.
That is why j should not be set to a constant value. Setting it to j=0 would cause the inner loop to start at the beginning of the message at every iteration.
I added two simple print() statements to your code to clarify:
def encode(message):
encoded_message = ""
i = 0
while(i<len(message)):
print(f'outer loop: i={i}')
count = 1
ch = message[i]
j = i
while(j<len(message)-1):
print(f'\tinner loop: j={j}')
if message[j] == message[j+1]: # if the previous and next characters are the same
count = count + 1 # we increase count variable
j += 1 # we increase j position
else:
break
encoded_message = encoded_message + str(count) + ch # "" + count converted to string + character (ch)
i = j + 1
return encoded_message
text = 'Hello World'
encoded_message = encode(text)
print('The encoded message is the output ', encoded_message)
(Please note: I do not know the RLE algorithm but just looked at your code.)