- 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
cup_swapping(["AB", "CA"]) ➞ "C" cup_swapping(["AC", "CA", "CA", "AC"]) ➞ "B" cup_swapping(["BA", "AC", "CA", "BC"]) ➞ "A"
- 1. initialise a current position "B"
- 2. iterate over the list of swap combination
- 2.1 iterate over each swap combination
- 3. check the ball have been swap
- 3.1 if current position is exist in the swap combination, it is swapped
- 3.2 update the current position
- 3.2.1 if current_position equals to the first letter
- 3.2.2 then final letter is the current position
- 3.3.1 if current_position not equal the first letter
- 3.3.2 then first letter is the current position
- 4. print the final position
def cup_swapping(swaps): current_position = "B" for move in swaps: if current_position in move: if current_position == move: current_position = move else: current_position = move return current_position
- shorten version of my answer
def cup_swapping(swaps): current_position = "B" for move in swaps: if current_position in move: current_position = move if move == current_position else move return current_position
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
- 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
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