You are playing a Flip Game with a friend.
You are given a string currentState consisting only of the characters '+' and '-'. Players take turns flipping two consecutive "++" into "--". The game ends when a player cannot make a move, at which point the other player wins.
Return all possible states of currentState after performing exactly one valid move. The answer may be returned in any order. If no valid move exists, return an empty list.
Constraints:
currentState.length
currentState[i] is either '+' or '-'
The main idea is to generate all possible valid next moves by scanning the string for every occurrence of two consecutive '+' characters. Whenever such a pair is found, we create a new state by flipping that "++" into "--" while keeping the rest of the string unchanged. Each newly formed state is then added to the result list.
Although this problem is often categorized as a backtracking problem, this solution mainly uses the enumeration part of backtracking. It systematically checks every possible position where a move can be made and generates the corresponding next state. Since each new state is created independently using string slicing, there is no need to modify the original string in place or perform an undo step.
Now, let's look at the solution steps below:
Initialize an empty list result to store all possible next states.
Iterate through currentState using an index i from len(currentState) - 2 (i.e., range(len(currentState) - 1)), examining each pair of consecutive characters.
At each index i, check whether both currentState[i] and currentState[i + 1] are '+'.
If they form a "++" pair, ...
You are playing a Flip Game with a friend.
You are given a string currentState consisting only of the characters '+' and '-'. Players take turns flipping two consecutive "++" into "--". The game ends when a player cannot make a move, at which point the other player wins.
Return all possible states of currentState after performing exactly one valid move. The answer may be returned in any order. If no valid move exists, return an empty list.
Constraints:
currentState.length
currentState[i] is either '+' or '-'
The main idea is to generate all possible valid next moves by scanning the string for every occurrence of two consecutive '+' characters. Whenever such a pair is found, we create a new state by flipping that "++" into "--" while keeping the rest of the string unchanged. Each newly formed state is then added to the result list.
Although this problem is often categorized as a backtracking problem, this solution mainly uses the enumeration part of backtracking. It systematically checks every possible position where a move can be made and generates the corresponding next state. Since each new state is created independently using string slicing, there is no need to modify the original string in place or perform an undo step.
Now, let's look at the solution steps below:
Initialize an empty list result to store all possible next states.
Iterate through currentState using an index i from len(currentState) - 2 (i.e., range(len(currentState) - 1)), examining each pair of consecutive characters.
At each index i, check whether both currentState[i] and currentState[i + 1] are '+'.
If they form a "++" pair, ...