Flip Game

class Solution {
public:
    vector<string> findNextMoves(string initial) {
        vector<string> possibleMoves;
        for (int i = 0; i < initial.length() - 1; i++) {
            if (initial[i] == '+' && initial[i + 1] == '+') {
                string modified = initial.substr(0, i) + "--" + initial.substr(i + 2);
                possibleMoves.push_back(modified);
            }
        }
        return possibleMoves;
    }
};

The "Flip Game" solution, implemented in C++, involves generating all possible moves from a given game state where consecutive '+' characters are flipped to '--'. The process is efficiently handled within a loop that iterates over the input string to check and replace each occurrence of '++'.

• Initialize a vector<string> to store the possible moves.
• Iterate over the string with a loop that checks each character and the one following it.
• If both characters are '+', construct a new version of the string where these two characters are replaced by '--'.
• Append this modified string to your list of possible moves.
• Finally, return the vector containing all possible states after one legal move.

This solution not only detects and modifies the game state efficiently but also ensures that all potential moves are considered. This makes it optimal for scenarios where it's crucial to evaluate multiple outcomes from a single game state. Remember, the approach guarantees that only valid transformations of the game state are generated.

class Solution {
    public List<String> flipGame(String inputState) {
        List<String> possibleFlips = new ArrayList<>();
        for (int i = 0; i < inputState.length() - 1; i++) {
            if (inputState.charAt(i) == '+' && inputState.charAt(i + 1) == '+') {
                String flipped = inputState.substring(0, i) + "--" + inputState.substring(i + 2);
                possibleFlips.add(flipped);
            }
        }
        return possibleFlips;
    }
}

The given Java code solves the problem "Flip Game", where the objective is to generate all possible states of a string after flipping two consecutive '+' characters to '--'. Here's a clear breakdown of the code functionality:

• Define a class named Solution.
• Inside this class, a method named flipGame accepts a string inputState as its parameter.
• A List<String> named possibleFlips is created to store all possible results after performing flips.
• Loop through the characters of inputState using a for loop that iterates until the second last character. This ensures that there are always two characters available for processing, avoiding an Index Out Of Bounds Exception.
• For each character position, check if the current and the next characters are both '+'.
• If both are '+', create a new string where the two '+' characters have been replaced by '--'. This is done by:
  • Taking a substring from the start of the string up to the current character.
  • Adding "--".
  • Concatenating the substring from the position right after the flipped characters to the end of the string.
• Add this new flipped string to possibleFlips.
• Once all possible flips are checked, return the possibleFlips list.

This code directly modifies sequences in the input string and collects all variations in a list to provide a solution set without altering the original state of the input.

char** computeNextMoves(char* inputState, int* sizeCounter) {
    *sizeCounter = 0;
    char** movesList = NULL;

    for (size_t i = 0; i < strlen(inputState) - 1; ++i) {
        if (inputState[i] == '+' && inputState[i + 1] == '+') {
            char* newState = malloc((strlen(inputState) + 1) * sizeof(char));
            strcpy(newState, inputState);
            newState[i] = '-';
            newState[i + 1] = '-';

            movesList = realloc(movesList, (*sizeCounter + 1) * sizeof(char*));
            movesList[*sizeCounter] = newState;
            ++(*sizeCounter);
        }
    }

    return movesList;
}

The provided C code defines the function computeNextMoves which generates all possible states of the game "Flip Game" from a given input state. The game involves flipping two consecutive '+' characters into '-' characters.

Here’s how the function operates:

• Initialize sizeCounter to 0, which tracks the number of valid moves.
• Create a movesList pointer initially set to NULL. This list will be dynamically allocated to store possible game states.
• Iterate over the input state using a loop. Check each character and the one following it.
  • If both characters are '+', craft a new game state based on the current input where the two '+' are flipped to '-'.
  • Allocate memory for the new state and copy the original input state into it.
  • Perform the flipping operation at the detected position.
  • Use realloc to resize movesList and add the new state to the list while updating sizeCounter.
• Finally, return the list of possible moves (new states) created from the input state.

Essentially, this function assists in exploring all potential moves in a given instance of the game by adjusting strings according to game rules. The function also dynamically manages the memory to store and return all possible game states efficiently. This enables further game state analysis or next move decisions based on the returned list of states.

var findNextMoves = function(state) {
    const allNextMoves = [];

    for (let idx = 0; idx < state.length - 1; ++idx) {
        if (state[idx] === '+' && state[idx + 1] === '+') {
            const newState = (
                  state.substring(0, idx) + 
                  "--" + 
                  state.substring(idx + 2)
            );
            allNextMoves.push(newState);
        }
    }

    return allNextMoves;
};

The solution to the Flip Game problem involves finding all the possible states of a string, after making a valid move. A valid move consists of flipping two consecutive "+" symbols into two "-" symbols.

The provided JavaScript function findNextMoves efficiently determines all these possible new states:

• Initialize allNextMoves, an array to hold all the possible states after the valid moves.
• Iterate through the string state using a loop. The loop evaluates if the current character and the next one are both '+':
  • If true, create a new string where the two '+' characters are replaced with '--'.
  • This new state is appended to the allNextMoves array.
• After completing the loop, return the allNextMoves array, which now contains all the potential next moves.

This function leverages string manipulation methods such as substring for crafting the new states and uses a simple for loop to check every possible pair of characters in the input string. The result is a straightforward and effective approach to generating game moves.

class Solution:
    def generateMoves(self, state: str) -> List[str]:
        result_moves = []

        for i in range(len(state) - 1):
            if state[i] == '+' and state[i + 1] == '+':
                modified_state = state[:i] + "--" + state[i + 2:]
                result_moves.append(modified_state)

        return result_moves

The given Python code defines a solution to the Flip Game problem, where the objective is to generate all possible states of a string of pluses and minuses after making a valid move. A valid move consists of flipping two consecutive '+' characters into '--'. Here's a breakdown of the implementation:

• A class named Solution contains the method generateMoves, which accepts a string state representing the current configuration of '+' and '-' characters.
• Within the method:
  • An empty list result_moves is initialized to store the resulting states after each valid move.
  • A for loop iterates through the string state until the second to last character, checking for consecutive '+' characters.
  • When a pair of consecutive '+' characters is found, a new string modified_state is created:
    • Characters before the pair are unchanged.
    • The pair of '+' is replaced by '--'.
    • Characters following the pair remain unchanged.
  • This modified_state is then added to the result_moves list.
• After the loop finishes examining all possible pairs, the method returns the result_moves list, which contains all the new game states after each possible flip.

Overall, this solution methodically checks for all pairs of consecutive '+' characters, creates a new game state for each valid move, and collects these states to be returned. The approach ensures that each potential move is considered, providing a comprehensive set of moves available from the current state.