Table of Contents
Question
- Create a function that returns the letter position where the ball final position is once the swapping is finish.
- There are three cups on a table, at positions A, B, and C. At the start, there is a ball hidden under the cup at position B.
- There will be several swap perform, represented by two letters.
- For example, if I swap the cups at positions A and B, this can be represented as
AB
orBA
.
Examples
cup_swapping(["AB", "CA"]) ➞ "C"
cup_swapping(["AC", "CA", "CA", "AC"]) ➞ "B"
cup_swapping(["BA", "AC", "CA", "BC"]) ➞ "A"
My solution
- initialise a current position "B"
- iterate over the list of swap combination
- iterate over each swap combination
- check the ball have been swap
- if current position is exist in the swap combination, it is swapped
- update the current position to another letter
- if current_position equals to the first letter
- the final letter is the current position
- if current_position not equal the first letter
- the first letter is the current position
- if current position is exist in the swap combination, it is swapped
- check the ball have been swap
- iterate over each swap combination
- print the final position
def cup_swapping(swaps):
current_position = "B"
for move in swaps:
if current_position in move:
if current_position == move[0]:
current_position = move[1]
else:
current_position = move[0]
return current_position
Solution by others
Method 1
- shorten version of my answer
def cup_swapping(swaps):
current_position = "B"
for move in swaps:
if current_position in move:
current_position = move[1] if move[0] == current_position else move[0]
return current_position
Method 2
def cup_swapping(swaps, current_position="B"):
for move in swaps:
current_position = move.replace(current_position, "") if current_position in move else current_position
return current_position
- key point
- iterate over each swap
- in the swap, there is two letter
- if the current position appear in the swap, replace that letter with empty string
- i.e. replace "AB" to "A" if current position is "A"
- and also update the current position to the remaining single letter
- if the current position do not appear in the swap, keep the current position
My reflection
- It is a good feeling to solve a problem without hint. First I got stuck when just write the code, then I try to solve the question by writing the algorithm down, it sudden feel much easier to think. Thus, I will make the habit the write down the algorithm first rather coding at first. Beside, I learn new way to shorten the if else statement
Credit
challenge found on edabit