ENGG1110 Project
Changelog
Rev. Date Description
v1.1 2024/11/06 P.5 [4] Fixed the wrong coloring of matching
candies in first round.
P.14 [5.5.2] Added the checking of empty cells for
Target cell at swap.
P.14 [5.5.4] Added clarification on how
findAndRemoveMatch() checking order.
P.22 [6.3.2] Added clarification on how the cascade
matching checking order.
P.25 [8] Elaborated the grading specification.
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ENGG1110 Problem Solving by Programming
The Chinese University of Hong Kong
2024-2025 Term 1
Project
Due Date: 2024/12/04 (Wed) 23:59
1. Introduction
Candy Crush is a popular match-three puzzle game in the world, originally released in
2012 for Facebook and later adapted for mobile platforms.
In the basic gameplay, the gameboard consists of a grid filled with various types of
candies, each represented by different shapes and colors. The player’s goal is to create
matches of three or more identical candies by swapping adjacent one. When a match is
made, the matched candies are cleared from the gameboard, and new candies will fall
down to fill the empty spaces. This sometimes leads to “chain reactions”, where new
matches are automatically created as the board refills.
Figure 1. Sample Gameplay. Snapshots from
https://www.flickr.com/photos/alper/10330168576
In this project, you will develop a Candy Crush game using the C programming
language. The project is structured in two phases: Part I focuses on implementing the
basic version of the game, while Part II builds upon the first part by adding advanced
features and additional gameplay mechanics.
You are required to complete the given source code main.c without modifying any
existing code (except otherwise specified) or introducing new libraries. Marks will be
deducted from every modification.
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2. Program Flow
Part I
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Part II
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3. Suggested Project Schedule
Part I (60%)
Week 10 InitGameBoard(), printGameBoard()
Week 11 AskForSwap()- Input/Validation, swap()
Week 12 FindAndRemoveMatch(), isGameOver()
Part II (40%)
Week 13/14 File I/O, applyGravity, fillEmpty(),Cascade
Week 14 Cascade
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4. Sample Runs for Part I
The following shows several examples of inputs and the resulting candy clearings. User
inputs are indicated by bold, highlighted underlined text. The matches found by the
function are in red font.
=====
New Round:
Enter the coordinate (row, column) of the candy:5 2
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):L
Vertical Match found at column 2!
Enter the coordinate (row, column) of the candy:0 2
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):D
Horizontal Match found at row 1!
=====
New Round:
=====
Enter the coordinate (row, column) of the candy:0 0
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):L
Move Out of Bound.
Please try again.
=====
New Round:
Enter the coordinate (row, column) of the candy:1 2
Empty Cell Selected.
Please try again.
=====
New Round:
Enter the coordinate (row, column) of the candy:4 5
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):D
Horizontal Match found at row 4!
Enter the coordinate (row, column) of the candy:2 3
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):R
Horizontal Match found at row 2!
Enter the coordinate (row, column) of the candy:0 4
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):R
Horizontal Match found at row 0!
Enter the coordinate (row, column) of the candy:1 5
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):U
Horizontal Match found at row 1!
Game Over! No more possible moves.
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5. Detailed Program Design Flow – Part I
In this project, you are required to follow exactly the output format specified. Using
other output formats will jeopardize your mark.
This program will
1. Read and initialize the game board from source
2. Display the game board
3. Allow the player to select a candy to swap
a. The player can only swap two candies at a time
b. The player will choose a candy by entering the coordinates (row, column)
c. The player will also input a direction (U for Up, D for Down, L for Left, R for
Right) to specify where to swap the selected candy.
4. Find and remove matches
a. After each swap, check for matches of three or more identical candies in
a row or column.
b. If a match is found, display a message indicating the match’s location,
remove the matched candies, and update the game board.
5. Check for a game-over condition
a. Check if no further matches are possible on the gameboard.
b. If the board has no possible moves left, display the message and end the
game.
5.1. Header files, Functions, and Variable Declarations
At the beginning of the main.c file, we include two headers, <stdio.h> and
<stdlib.h>.
No other header files or library are allowed in the project.
We define several macros after the header line. Macros are identifiers defined by
#define, which are replaced by their value before compilation. The first two are H and W.
#define H 6 // height
#define W 6 // width
H is the height of the game board, while W is its width. Therefore, our Candy Crush game
board is a 6x6 square. In our test cases, we do not have any test cases with varying board
size. You may try it if you are interested.
Each cell on the game board stores a candy, with different types of candies represented
by numbers. To assist in converting these numbers into their corresponding candy
representations, the following global variable is provided.
char candies[] = {'*', '#', '@', '%'};
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No other global variables are permitted. All variables you define must be declared
within functions and passed as parameters or return values as necessary. Violations of
this rule will result in a deduction of marks.
Also, there are a number of helper functions declared in the project. You can add new
functions to aid your work, but you CANNOT modify (function signatures – function
names, return type, parameters), or delete the given functions.
5.2. Main Function
The main function is given to control the game flow.
There are some local variables already declared for you. You can declare your own local
variables for your use.
Variables Usages
int board[H][W] Stores the candies on the game board.
The main function controls the gameplay as follows:
1. Call initGameBoard() to load the initial game board.
2. Enter the main game loop. The loop should continue until the game is over. Here
are the tasks in the loop.
a. The loop should start by printing five equal signs (=====) as a separator
for each round, as follows:
=====
New Round:
b. Then, call printGameBoard() to display the current game board.
c. Call askForSwap() to execute the swapping logic. If the askForSwap()
returns zero (0), indicating the swapping is unsuccessful. In this case,
print the following error message:
Please try again.\n
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d. Call isGameOver() to check if any moves are possible. If no valid moves
remain, display a game over message and exit the game loop. In this case,
print the following error message:
Game Over! No more possible moves.\n
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5.3. Initializing Game Board
The main() function will first call the initGameBoard() function, which initializes the
board[] array for the later gameplay. In Part I, the content of the array should be read
from another hard-coded arrays – board_samples[].
5.4. Print Game Board
The given printGameBoard() is useful throughout the program to show the current
game board status to the user. You are required to implement this function and print the
game board on the screen based on the following format, where ␣ represents a space
character that should appear as an actual space in the program output.
First, print a line of five equal signs (=====) as a separator. Then, display the game board
with row and column numbers labeled. Each cell should be separated by spaces and
vertical bars to clearly distinguish rows and columns.
=====
␣␣|␣0␣|␣1␣|␣2␣|␣3␣|␣4␣|␣5␣|
␣0|␣#␣|␣%␣|␣@␣|␣*␣|␣#␣|␣*␣|
␣1|␣@␣|␣@␣|␣*␣|␣#␣|␣#␣|␣%␣|
␣2|␣#␣|␣%␣|␣%␣|␣@␣|␣%␣|␣*␣|
␣3|␣%␣|␣*␣|␣@␣|␣#␣|␣*␣|␣@␣|
␣4|␣#␣|␣*␣|␣@␣|␣%␣|␣%␣|␣@␣|
␣5|␣%␣|␣@␣|␣#␣|␣*␣|␣%␣|␣%␣|
There are two types of elements displayed on the grid:
• Candies: Use the candies[] character array to convert the numerical
values stored in board[][] into the corresponding candy symbols.
• Empty Space: Display the space character (' '), which is stored in
board[][] as ASCII ** (space).
It is crucial that your output format follows the example exactly, including the number
of spaces and any other formatting details, as the program will be graded using an
autograder. Any deviation in the format could result in a loss of marks.
5.5. Ask for input for swapping
The main function will call askForSwap() to handle the game action. The swapping
logic will be implemented inside this function. This function will return an integer to
indicate whether the swapping is successful or not. (Details of return value)
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5.5.1. User Input
5.5.1.1. Coordinates
The function should first ask the users for input two integers for the coordinates first:
Enter the coordinate (row, column) of the candy:\n
After receiving the user input, validate the input based on numerical correctness. You
can assume the user will only input integers. Ensure that the coordinates are within the
valid game board range. If the coordinates input is out of bounds, output the following
error message and return zero (0).
Coordinates Out of Bound.\n
5.5.1.2. Empty Cells
Then, the function should check whether the selected cell is empty or not. If the cell is
empty, output the following error message and return zero (0).
Empty Cell Selected.\n
5.5.1.3. Direction to Swap
After the coordinates are valid, the game should ask for the direction:
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):\n
You can assume that the user will input one character only. This input should be
validated to ensure it is correct – i.e. Upper case and should be one of the four
possibilities (U,D,L,R).If the direction is incorrect, output the following error message
and return zero (0).
Wrong Direction Input.\n
5.5.2. Valid Swapping Check
When attempting to move a candy, the program should validate that the move stays
within the boundaries of the game board, For example, the candy at position (0, 0)
cannot be swapped to the left, as it is already at the left boundary of the board
If the move is out of bounds, output the following error message and return zero (0).
Move Out of Bound.\n
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In addition, the program should also check the Target cell (e.g. if swapping (1,3) to the
left, Target cell is (1,2)) is empty. In this case, output the following error message and
return zero (0).
Empty Cell Selected.\n
5.5.3. Execute Swap
If the input validations pass, the swap action is performed by calling the swap()
function. You should implement the swap() to take the board, the starting coordinate,
the target coordinate, and the direction as arguments. The function will then swap the
selected candies in the specified direction. For example, if the direction is U (up), the
candy at (row,col) will be swapped with the candy directly above it at (row-1, col).
Similarly, if the direction is L (Left), the candy at (row, col) will be swapped with the
candy to the left (row,col-1). After the swap, you may use printGameBoard() to
inspect the result, but remember to remove this call after completing your inspection.
5.5.4. Find and Remove Matches
After the swapping, the findAndRemoveMatch() function is called to locate any
matches involving the candy at both the target position and the original position, as a
match may form in either direction. The function checks the neighboring cells around
each of these positions to detect any sequence of three or more identical candies
horizontally or vertically.
To facilitate auto-grading and maintain consistency, you should check the matches in
the following order.
1. Order of Checks: When checking for matches, start with the Target Position
(where swap has just placed a new candy). After completing all the checks and
removal at the Target Position, move to the Start Position (the original cell where
the candy was swapped from) and perform the same operations.
For example, swapping (1,2) downwards: Target Position is (2,2); and the Start
Position is (1,2).
2. Horizontal Matches: Starting for the given cell, if it is not empty (‘ ’), check to
the left (if any) to see if there are three or more consecutive identical candies in
the same row. Then check the right direction (if any).
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3. Vertical Matches: From the given cell, if it is not empty (‘ ’), check upwards (if
any) to see if there are three or more consecutive identical candies in the same
column. Then check the bottom direction (if any).
If a match is found in the horizontal/vertical direction, output the corresponding
message on the screen and indicate the row and column where the match occurred.
Horizontal Match found at row <Row Index>!\n
e.g. Horizontal Match found at row 1!
Vertical Match found at col <Column Index>!\n
e.g. Vertical Match found at column 1!
After finding the match, the game should remove the matching candies from the game
board. This is the intermediate status of the board after the removal.
Enter the coordinate of the candy you want to swap:5 1
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):R
Vertical Match found at col 2!
If the swap yields no matches, you should restore the game board to the previous status
(before the swap), print the message “No Match Found”, and return zero (0). Here is the
example:
Enter the coordinate of the candy you want to swap:0 0
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):R
No Match found!
In this function, you should return one (1) to the caller – i.e. AskForSwap() function.
5.6. Game Over Checking
As the game progresses, there will be eventually no more matches in the game board.
you should implement isGameOver() to check the whole board to see if there is at
least one potential match or not.
You can try swapping each candy with its right neighbour (if any) and its bottom
neighbour (if any). After the swap, matches may be formed in any four directions (Up,
Down, Left, Right). Therefore, you will implement a helper function isMatching() to
do the checking. This function will do a simple checking to see if there is at least one
match-three that can be formed by the given cell in any of the directions. It shall return
one (1) if there is at least one match; If there is no match found, return zero (0).
You may need to call it twice to check both the original position and swapped position
for any potential matches.
After each check, immediately undo the swap to restore the board to its original state.
If a match is found during any swap, return one (1); If no matches are possible after all
check, return zero (0). The main function will check this status and
The following input can be used to check the game over status:
Enter the coordinate (row, column) of the candy:0 5
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):D
Horizontal Match found at row 1!
Game Over! No more possible moves
The main() function will handle this, print out the error message,
Game Over! No more possible moves.\n
and will eventually terminate the game loop.
** End of Part I **
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6. Detailed Program Design Flow – Part II
In the part, we will extend the work of Part I to enhance the program functionality. Make
a copy of your source code of Part I. You will need to submit another source code for
Part II.
6.1. Main Function
In the main function, three more variables are introduced for the next section.
int stacks[100] stores the extra candies, which are used
to fill empty spaces after matched
candies are removed. Maximum 100
candies can be stored.
numCandies Represents the total number of candies
available in the stacks[] array for
refilling the board.
current Acts as a pointer or counter that keeps
track of the current candy being used
from stacks[] to refill the board during
gameplay. The current variable will be
initialized to 0 and will be incremented as
each candy is used during gameplay.
6.2. Read board and stacks from file
Previously in Part I the game board and stacks are read from hard-coded arrays for
easier debugging. Now let’s extend the function to file I/O and give us flexibility to
replace the game board to a different initial status.
The main() function will first call the initGameBoardFromFile() function, which
initializes these arrays. The contents of the arrays should be read from a file named
“board.txt”. Finally the function should return the number of candies in the stack,
which will be stored in the numCandies variable in the main function.
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Below is an example of the expected format for “board.txt”:
• First Line: Contains two integers representing the game board dimensions – the
number of rows r and columns c.
• Next r Lines: A grid of r x c integers representing the initial game board. Each
integer corresponds to a candy type.
• Following Line: Contains a single integer n, which corresponds to numCandies
and represents the total number of extra candies in the stacks[].
• Final Line: A list of n integers, each representing an extra candy that will be used
to fill the board when matches are removed.
Please ensure that the file is read correctly, and handle file operations properly. If an
error occurs (e.g., the file cannot be opened), output the following message and
terminate the program with an exit code of -1.
Failed to open board.txt!\n
6.3. Applying Gravity
There will be empty cells after the candy’s removal.
You should implement the gravity algorithm in the applyGravity() function for
simulating “gravity”. The main() function will call this function if the swapping is
successful – i.e. the return value of askForSwap() is non-zero.
In this function, implement the gravity feature to shift candies downwards into empty
spaces.
Starting from the bottom of the each column, the function should upward to find empty
spaces (represented by ASCII ** ‘ ’). When such empty space is detected, shift any
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candies above it down by one row . Repeat this process until each column has no empty
space remaining below any candies.
At the end of the applyGravity(), call printGameBoard() to output the game board.
In this example, the candies at the top of column 2 should fall down to fill the empty
spaces below. and the result should look like this:
At this point, you do not have to do the match checking.
6.3.1. Fill Empty Spaces
After candies are removed from the board, empty spaces will be left behind, which need
to be refilled after applying the gravity. The main function will call fillEmpty() to fill
these spaces using the candies stored in the stacks[] array after applying the gravity.
You can track the current position in the array using the current variable, which
indicates where the next candy should be retrieved from.
As you retrieve candies from the array, fill the empty spaces from bottom-to-top, left-to -
-right manner to simulate the real candy crush.
At last, call printGameBoard() to show the board status.
Here is the status after the candy removal, just before the gravity application and candy
refill.
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After calling fillEmpty() in the main() function, you should see the following:
Once the original candies have fallen to the bottom (highlighted in yellow above), any
remaining empty spaces are refilled sequentially using candies from the stacks[] array.
The current variable in the parameter keeps track of the position in stacks[] from where
the next candy should be drawn. Each time after the candies is drawn, current is
incremented to point to next candies.
Here is the example of how current variable works with the stacks[]. After the
beginning of the game, the current variable is set to zero (0) to indicate the candy drawn
next is the first item in the stack.
current = 0
1 2 3 3 2 1 1 0
After one candy is drawn for refill, the current variable is incremented to one (1) such
that next candy drawn is the second item in the stacks[].
current = 1
1 2 3 3 2 1 1 0
In the game, this is the array that helps you to convert the number to the candy
representation.
char candies[] = {'*', '#', '@', '%'};
With this array, you can observe that the empty cells are filled with “#”, “@” and “%”
from bottom to top, which is 1,2,3 in the stacks array respectively.
The process will continue until all the candies in the stack are exhausted. When filling
the candy, if the number of candies remaining in the stacks[] is less than the number of
empty spaces on the board, the game will be unable to fill all spaces. In this case, the
game should display an error message and terminate the program with an exit code of -
1.
No more candies available.
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This check will naturally handle both cases: if stacks[] is exhausted during normal game
play, or if stack[] is empty from the very beginning, as both conditions would trigger the
same error and exit the program at this point.
If multiple columns contain empty spaces, fill these spaces in a bottom-to-top order
within each column, moving from the leftmost column to the rightmost column. Here is
the example of the case of filling in multiple column spaces. The number in red italic
and brackets indicates the filling sequence.
6.3.2. Cascade Matching
When the candies are refilled, new matches may form on the board. To mimic real
gameplay, the game should continuously check for new matches as the board refills,
repeating the process until the board is stable with no further matches.
The main function will call cascade() function right after the matching process. Within
the function, you should call both the applyGravity() and fillEmpty() for the
cascade process. As a result, any previous calls to these functions in the main function
should be removed, as they are now called within cascade().
In the cascade function, you are required to check if there are any matches for each
cell. For this, you will call findMatchAndRemove() function (developed in part I) to find
all matches on each non-empty cell. You can make use of the return value of
findMatchAndRemove() to determine whether a match is found.
In the cascade function, repeat the process until no further matches can be found in the
board. In each checking round:
1. Apply the gravity.
2. Fill in all the empty cells on the board and get the updated value of current
3. Print the Gameboard to show the current status
4. Remove all matches found on the board. Starting from the top-left corner (0,0),
check each cell for matches in the following order:
a. Row by Row, Column by Column: For each cell, proceed across each row
from left to right, then move down to the next row.
b. Check Directions: For each cell, check for matches in the order of Left,
Right, Top, and Bottom
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c. Clear Matches: If a match is found, clear the matching candies
immediately before proceeding to the next cell.
5. If there is any removal, output the following at the end of checking:
Cascade Matches found!\n
6. After the cascade checking completes with no further matches, return the
updated value of current to the main() function.
Repeat these steps until no matches are left, ensuring that all cascading actions are
completed before returning to the main function.
Below is the sample of a cascade matching, the matches found by the cascade function
are in red font.
=====
New Round:
=====
Enter the coordinate (row, column) of the candy:1 2
Enter the direction to swap (U for Up, D for Down, L for Left, R
for Right):U
Horizontal Match found at row 1!
=====
Vertical Match found at column 0!
Cascade Matches found!
Horizontal Match found at row 2!
Cascade Matches found!
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7. Academic Honesty and Declaration Statement
Attention is drawn to University policy and regulations on honesty in academic work,
and to the disciplinary guidelines and procedures applicable to breaches of such policy
and regulations. Details may be found at
https://www.erg.cuhk.edu.hk/erg/AcademicHonesty .
You are required to fill in the following declaration statement as the comment at the
beginning of the main.c source code with your information. Assignments without the
properly signed declaration will not be graded.
Tools such as software similarity measurement, AI-tool fingerprint detection, etc., might
be used to inspect all submissions.
/**
* ENGG1110 24R1 Problem Solving by Programming
*
* Course Project
*
* I declare that the project here submitted is original
* except for source material explicitly acknowledged,
* and that the same or closely related material has not been
* previously submitted for another course.
* I also acknowledge that I am aware of University policy a nd
* regulations on honesty in academic work, and of the disciplinary
* guidelines and procedures applicable to breaches of such
* policy and regulations, as contained in the website.
*
* University Guideline on Academic Honesty:
* https://www.cuhk.edu.hk/policy/academichonesty/
*
* Student Name :
* Student ID :
* Class/Section :
* Date :
*/
8. Grading Platform and Submission
We will grade your work in Gradescope autograder. Please note that while passing the
test cases is necessary, it is not sufficient on its own for full marks. Additional marks will
be allocated based on the completeness and adherence to all requirements specified in
the project documentation, including code organization, functionality, and adherence
to the design specifications.
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Please follow the steps below to submit your work by the deadline.
1. Rename the modified main.c for part I to main_part1.c
2. Rename the source code for part II to main_part2.c
3. Submit your .c file to the Gradescope.
Please only submit the source file (.c). You may submit many times before the due date,
but the latest attempt will be graded.
9. Late Submission
The late submission penalty is as follows:
• Within 3 days (72 hours): 10% per 24 hours
• 3-7 days: 50% penalty
• More than 7 days: 100% penalty (Your work will not be graded)
NOTE: Submitting the project is crucial in PASSING the course.
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