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A function in my program seems like it should work but occasionally gives the wrong output

I wrote a function that checks for a given cell in a grid if it is a legal move following the rules of the board-game called Reversi otherwise known as Othello. The rules are that a circle can only be placed on the grid whenever the newly placed circle and a previous placed circle bounds one of the opponents circles. The majority of the time the function gives the right output (i.e. true when it is a legal move and false when it is a legal move), but some moves that are legal by the previously stated rules are not deemed as a legal move by the function.
I've tried to use the console to check at every step at which cell the function is currently looking and what the value of the cell is to determine what goes wrong. This has only led me to being even more confused.
The following code is the doomed-function:
bool legalMove(int row, int col)
{
// Check if the cell is occupied
if (board[row,col] != 0)
return false;
// Check if there's an opponents circle somewhere around it
for (int i = -1; i<=1; i++)
for (int j = -1; j<=1; j++)
{
if (i == 0 && j == 0)
continue;
int currentRow = row + i;
int currentCol = col + j;
if (currentRow >= 0 && currentRow < board.GetLength(0) && currentCol >= 0 && currentCol < board.GetLength(1) && board[currentRow,currentCol] == -turn)
{
// Now we know that there's an opponents circle somewhere around this space, we now check if it can be captured
while(true)
{
currentRow += i;
currentCol += j;
Console.WriteLine($"currentRow: {currentRow}, currentCol: {currentCol}, value: {board[currentRow,currentCol]}");
if (currentRow < 0 || currentRow >= board.GetLength(0) || currentCol < 0 || currentCol >= board.GetLength(1) || board[currentRow, currentCol] == 0)
return false; // Outside of the board or an empty space
else if (board[currentRow,currentCol] == turn)
return true; // No empty spaces between our cell and another cell of ours
}
}
}
return false; // No cell found around ours
}
What am I missing here?
Thanks in advance!
EDIT:
The entire program is the following (hope it can help):
/* TO-DO
* Make function out of no legal move and tidy up
* Calculate amount of circles of player to determine the winner
* Make victory label better
!!!Tidy up flipCircles method and fix legalMove method
Create a slider and make it change the gridSize
Make GUI change empty space when board gets smaller or bigger
Tidy up the 2x calling to check what the score is
*/
// Library imports
using System;
using System.Drawing;
using System.Security.Policy;
using System.Windows.Forms;
// Game class
class Game : Form
{
// Declare variables
private Board board;
private Button newGame, help;
private Font font;
private Label countRed, countBlue, gameState;
private TrackBar sizeBoard;
public int gridSize = 6;
public Game()
{
// Set the form properties
ClientSize = new Size(520, 670); Text = "Reversi";
// Creating the GUI and adding it to the form
newGame = new Button(); Controls.Add(newGame);
help = new Button(); Controls.Add(help);
font = new Font("Arial", 14);
countBlue = new Label(); Controls.Add(countBlue); countBlue.Font = font;
countRed = new Label(); Controls.Add(countRed); countRed.Font = font;
gameState = new Label(); Controls.Add(gameState); gameState.Font = font;
board = new Board(gridSize); Controls.Add(board);
// Settings of the GUI
newGame.Size = new Size(100, 30); newGame.Location = new Point(150, 10); newGame.Text = "New Game"; newGame.BackColor = Color.LightSlateGray;
help.Size = new Size(100, 30); help.Location = new Point(270, 10); help.Text = "Help"; help.BackColor = Color.LightSlateGray;
countBlue.Size = new Size(110, 30); countBlue.Location = new Point(150, 50); countBlue.Text = $"{board.countBlue} stones"; countBlue.ForeColor = Color.CornflowerBlue;
countRed.Size = new Size(110, 30); countRed.Location = new Point(150, 90); countRed.Text = $"{board.countRed} stones"; countRed.ForeColor = Color.Firebrick;
gameState.Size = new Size(150, 30); gameState.Location = new Point(270, 90); gameState.Text = $"{board.playersTurn}";
// Events //
// Label events
newGame.Click += reset;
help.Click += calculateHelp;
// Board events
board.MouseClick += clicked;
//Paint event
Paint += paint;
}
// Event-handlers //
// Label event-handlers
private void reset(object e, EventArgs ea)
{
board.Reset();
countBlue.Text = $"{board.countBlue} stones";
countRed.Text = $"{board.countRed} stones";
gameState.Text = $"{board.playersTurn}";
}
private void calculateHelp(object e, EventArgs ea)
{
board.SetHelp();
}
// Board event-handlers
private void clicked(object e, MouseEventArgs mea)
{
board.Clicked(mea.Location);
countBlue.Text = $"{board.countBlue} stones";
countRed.Text = $"{board.countRed} stones";
gameState.Text = $"{board.playersTurn}";
// Now check if there's a legalMove if not
//if (timesNoLegalMove > 1)
gameState.Text = $"{board.playersTurn}";
}
// Paint event-handler
private void paint(object e, PaintEventArgs pea)
{
Graphics gr = pea.Graphics;
gr.FillEllipse(Brushes.CornflowerBlue, 100, 45, 31, 31);
gr.FillEllipse(Brushes.Firebrick, 100, 85, 31, 31);
}
}
// Board class
class Board : Label
{
// Declare all global variables used in this class
private int[,] board;
private int size;
private int turn = 1; // 1 is blue, -1 is red
private bool legalMoveExists = true;
public int timesNoLegalMove = 0;
private bool help = false;
// Create the board and set settings + events
public Board(int gridSize)
{
size = gridSize;
Size = new Size(size * 50, size * 50);
Location = new Point(10 + (25 * (10 - size)), 120 + (25 * (10 - size)));
BackColor = Color.White;
board = new int[size, size];
startingState();
Paint += Draw;
}
// Sets the values of the center 4 squares to that of the starting circles
private void startingState()
{
board[(size / 2)-1, (size / 2)-1] = 1;
board[(size / 2), (size / 2)] = 1;
board[(size / 2), (size / 2) - 1] = -1;
board[(size / 2) - 1, (size / 2)] = -1;
}
// Resets the board when New Game is clicked
public void Reset()
{
for (int row = 0; row < board.GetLength(0); row++)
for (int col = 0; col < board.GetLength(1); col++)
board[row, col] = 0;
startingState();
turn = 1;
Invalidate();
}
public void SetHelp()
{
if (help)
help = false;
else
help = true;
Invalidate();
}
public string playersTurn
{
get
{
if (turn == 1)
return "It's Blue's turn";
if (turn == -1)
return "It's Red's turn";
else
{
if (countBlue > countRed)
return "Blue has won the game!";
if (countRed > countBlue)
return "Red has won the game!";
else
return "It's a draw!";
}
}
}
public int countRed
{
get
{
return board.Cast<int>().Count(n => n == -1);
}
}
public int countBlue
{
get
{
return board.Cast<int>().Count(n => n == 1);
}
}
bool legalMove(int row, int col)
{
// Check if the cell is occupied
if (board[row,col] != 0)
return false;
// Check if there's an opponents circle somewhere around it
for (int i = -1; i<=1; i++)
for (int j = -1; j<=1; j++)
{
if (i == 0 && j == 0)
continue;
int currentRow = row + i;
int currentCol = col + j;
if (currentRow >= 0 && currentRow < board.GetLength(0) && currentCol >= 0 && currentCol < board.GetLength(1) && board[currentRow,currentCol] == -turn)
{
// Now we know that there's an opponents circle somewhere around this space, we now check if it can be captured
while(true)
{
currentRow += i;
currentCol += j;
if (currentRow < 0 || currentRow >= board.GetLength(0) || currentCol < 0 || currentCol >= board.GetLength(1) || board[currentRow, currentCol] == 0)
return false; // Outside of the board or an empty space
else if (board[currentRow,currentCol] == turn)
return true; // No empty spaces between our cell and another cell of ours
}
}
}
return false; // No cell found around ours
}
private void flipCircles(int row, int col)
{
// Check all eight directions from the current position
for (int r = row - 1; r <= row + 1; r++)
{
for (int c = col - 1; c <= col + 1; c++)
{
// Skip the current position
if (r == row && c == col)
continue;
int rr = r;
int cc = c;
// Check if the next position in this direction is a valid position on the board
// and if it is occupied by the opponent's piece
if (rr >= 0 && rr < board.GetLength(0) && cc >= 0 && cc < board.GetLength(1) && board[rr, cc] == -turn)
{
// Keep moving in this direction until we find the current player's piece or an empty cell
while (true)
{
rr += r - row;
cc += c - col;
// If we have reached an invalid position or an empty cell, break out of the loop
if (rr < 0 || rr >= board.GetLength(0) || cc < 0 || cc >= board.GetLength(1) || board[rr, cc] == 0)
break;
// If we have found the current player's piece, flip all the pieces between the current position and the player's piece
if (board[rr, cc] == turn)
{
while (rr != r || cc != c)
{
rr -= r - row;
cc -= c - col;
board[rr, cc] = turn;
}
break;
}
}
}
}
}
}
// Sets the value of a clicked cell to either 1 (Blue), or -1 (Red)
public void Clicked(Point mea)
{
int rowClicked = mea.X / 50;
int colClicked = mea.Y /50;
if (legalMove(rowClicked, colClicked))
{
board[rowClicked, colClicked] = turn;
flipCircles(rowClicked, colClicked);
help = false;
turn = -turn;
legalMoveExists = false;
Invalidate();
}
}
// Draws the entire board and all circles
void Draw(object e, PaintEventArgs pea)
{
Graphics gr = pea.Graphics;
legalMoveExists = false;
for (int row = 0; row < board.GetLength(0); row++)
for (int col = 0; col < board.GetLength(1); col++)
{
// Draw the background tiles
if (row % 2 == 0 && col % 2 == 0 || row % 2 != 0 && col % 2 != 0)
gr.FillRectangle(Brushes.DarkGray, 50 * row, 50 * col, 50, 50);
// Draw circles
if (board[row, col] == 1) // Blue circles
gr.FillEllipse(Brushes.CornflowerBlue, 50 * row - 1, 50 * col - 1, 51, 51);
else if (board[row, col] == -1) // Red circles
gr.FillEllipse(Brushes.Firebrick, 50 * row - 1, 50 * col - 1, 51, 51);
// Check for legal moves and draw help circles if the help button has been pressed
else if (legalMove(row, col))
{
legalMoveExists = true;
timesNoLegalMove = 0;
if (help) // Help circles
gr.DrawEllipse(Pens.Black, 50 * row + 9, 50 * col + 9, 31, 31);
}
}
// Make this a function
if (!legalMoveExists)
{
turn = -turn;
timesNoLegalMove++;
Invalidate();
if (timesNoLegalMove > 1)
turn = 0;
}
}
}
// Main run
class Program
{
static void Main()
{
Application.Run(new Game());
}
}

Your question states that the function you wrote to scan the surrounding cells is failing sporadically and that it's difficult to diagnose. It was easy to reproduce the failures by running your code, but I wasn't able to see an obvious way to effectively debug it.
It "might" be more effective to improve the algorithm where it's more methodical in how it inspects the surrounding cells in the first place, which would also be easier to debug if necessary. One solid way to do this would be to use custom Iterators where you could use a standard foreach pattern to inspect virtual "lines" radiating in the eight directions. At each 'yield' you can check to see whether a determination can be made in terms of either a "legal move" or a "capture".
Here's a proof-of-concept grid that is intended to demonstrate how the iterators work. It doesn't evaluate the cells in terms of game play in any way but you can see how it would lend itself to doing that. The idea here is to click any cell and observe the markup of U-R-D-L. It may also help to see it working so you can clone this sample and set breakpoints.
Left, Right, Up, Down iterator examples are shown - diagonals would follow the same pattern. The mouse down control passes the starting cell coordinate position as a Point:
public IEnumerable<Point> CellsUp(Point point)
{
while (true)
{
point = new Point(point.X, point.Y - 1);
if (point.Y < 0) break;
yield return point;
}
}
public IEnumerable<Point> CellsRight(Point point, int max)
{
while (true)
{
point = new Point(point.X + 1, point.Y);
if (point.X == max) break;
yield return point;
}
}
public IEnumerable<Point> CellsDown(Point point, int max)
{
while (true)
{
yield return point;
point = new Point(point.X, point.Y + 1);
if (point.Y == max) break;
}
}
public IEnumerable<Point> CellsLeft(Point point)
{
while (true)
{
yield return point;
point = new Point(point.X - 1, point.Y);
if (point.X < 0) break;
}
}
The code lays the groundwork for a methodical scan outward from any given point.
private void legalMoveIterationStub(object? sender, EventArgs e)
{
clear();
if(sender is Control control)
{
control.BackColor = Color.Blue;
control.Refresh();
var pos = board.GetCellPosition(control);
var pt = new Point(pos.Column, pos.Row);
Control ctrl;
foreach (var point in CellsUp(pt))
{
ctrl = board.GetControlFromPosition(point.X, point.Y);
ctrl.Text = "U";
ctrl.Refresh();
Thread.Sleep(DEMO_DELAY_MS);
// This is where the cell inspects e.g. for "empty square"
// or color. Chances are, some condition will be met
// and you will break from here rather than iterate
// all the way to the edge of the board each time.
}
foreach (var point in CellsRight(pt, board.ColumnCount))
{
ctrl = board.GetControlFromPosition(point.X, point.Y);
ctrl.Text = "R";
ctrl.Refresh();
Thread.Sleep(DEMO_DELAY_MS);
}
foreach (var point in CellsDown(pt, board.ColumnCount))
{
ctrl = board.GetControlFromPosition(point.X, point.Y);
ctrl.Text = "D";
ctrl.Refresh();
Thread.Sleep(DEMO_DELAY_MS);
}
foreach (var point in CellsLeft(pt))
{
ctrl = board.GetControlFromPosition(point.X, point.Y);
ctrl.Text = "L";
ctrl.Refresh();
Thread.Sleep(DEMO_DELAY_MS);
}
}
}
The demo board has been mocked like this for testing purposes:
public partial class Game : Form
{
public Game()
{
InitializeComponent();
for (int col = 0; col < board.ColumnCount; col++)
{
for (int row = 0; row < board.RowCount; row++)
{
var tile = new Label
{
BorderStyle = BorderStyle.FixedSingle,
Anchor = (AnchorStyles)0xF,
Margin = new Padding(1),
TextAlign = ContentAlignment.MiddleCenter
};
board.Controls.Add(tile, col, row);
tile.MouseDown += legalMove;
}
}
}
void clear()
{
foreach (Control control in board.Controls)
{
control.Text = string.Empty;
control.BackColor = SystemColors.Control;
}
board.Refresh();
}
.
.
.
}

Slow update time with tiles and MouseState MonoGame

Very new developer here.
In my program I have a randomly generating world map using a simplex noise library. On top of this I am attempting to draw a tilemap of transparent 4x4 tiles that appear slightly translucent when the mouse is hovering over one.
I've got this working but it takes about 3 whole seconds for the highlighted tile to update to the mouse's current position. Is there anything I could do to solve this?
This is my code for the MouseState check in the tile class:
public override void Update(GameTime gameTime)
{
_previousMouse = _currentMouse;
_currentMouse = Mouse.GetState();
var mouseRectangle = new Rectangle(_currentMouse.X, _currentMouse.Y, 1, 1);
_isHovering = false;
if (mouseRectangle.Intersects(Rectangle))
{
_isHovering = true;
if (_currentMouse.LeftButton == ButtonState.Released && _previousMouse.LeftButton == ButtonState.Pressed)
{
Click?.Invoke(this, new EventArgs());
}
}
}
Sorry if this is formatted wrong or badly asked, first post so still getting to grips with everything :)

Invert the logic:
Instead of checking thousands of tile objects against the mouse, apply the mouse to a single object.
Assuming you have a list or array of tile objects:
Add a new object to check for mouse hover and click:
public class MouseDetect(Tile[] tiles) // replace with List<> as needed
{
int PrevHover = -1; // used to unHover
// if (Area == Screen) make the next two lines `const`, so the compiler will remove all uses...
int AreaX = 0; //Area x offset
int AreaY = 0; //Area y offset
int AreaW = 800; //Area width
int AreaH = 480; //Area height
const int Grid = 4; // assumes square
const int GridW = AreaW / Grid;
// I Will assume the `Delegate Click` in `Tile` is public
public void Update(MouseState ms, MouseState oms), //_currentMouse = ms and _previousMouse = oms;
{
int mouseIndex = (ms.X - AreaX) % Gridw + (ms.Y - AreaY) / GridW;
tiles[PrevHover].Hover = false;
PrevHover = mouseIndex;
tiles[PrevHover].Hover = true;
//Check Release
if(tiles[PrevHover].Hover && ms.LeftButton == ms.ButtonState.Released && oms.LeftButton == ButtonState.Pressed)
tiles[PrevHover].Click(tiles[PrevHover], new EventArgs());
}
}
Remove the Update from the Tile class.
Notes for anyone reading this later:
Never call Mouse.GetState(); more than once per step.
Predefined or framework names such as Rectangle should never be used as an identifier.
i.e renamed and corrected to CollRectangle
if (CollRectangle.Contains(ms.Position))

Tilemap Index out of bounds collision

I created my tile map and my player with movement.
I'm now trying to create the collision and I feel i'm on the right track.
Here is how I've created the map.
List<Texture2D> tileTextures = new List<Texture2D>();
int tileWidth = 60;
int tileHeight = 60;
public int[,] Map = new int[,]
{
{2,2,2,2,2,2,2,2,2,2},
{2,2,2,2,1,2,2,2,2,2},
{2,2,2,2,2,2,2,2,2,2},
{2,2,2,2,2,2,2,2,2,2},
};
public void Draw(SpriteBatch spriteBatch)
{
int tileMapWidth = Map.GetLength(1);
int tileMapHeight = Map.GetLength(0);
for (int x = 0; x < tileMapWidth; x++)
{
for (int y = 0; y < tileMapHeight; y++)
{
int textureIndex = Map[y, x];
Texture2D texture = tileTextures[textureIndex];
spriteBatch.Draw(
texture,
source = new Rectangle(x *myTile.Width,
y * myTile.Height,
tileWidth,
tileHeight),
Color.White);
}
}
}
I am checking the 2d array coords with this condition and checking to see if a specific tile is there, where I can then set my previous location if it is true.
I'm currently testing on 1 tile atm.
public void Update(GameTime gameTime)
{
prevPosition = position;
input(gameTime);
if(tiles.Map[(int)playerPosition.X/60,(int)playerPosition.Y/60] == 1)
{
position = prevPosition;
}
}
However my player position keeps going out of the index bounds of the 2D array and I believe I need to scale it down so that it stops this, I've tried dividing the play coords by the width of the tiles but that hasn't worked.
If anyone can help me with the correct scaling I would be very appreciative.

This will happen if your player's position is like -x,y or x,-y or maybe -x,-y. Yor approach might be better if you'd make a fuction like this one
public bool CollidesWithWall(int x, int y)
{
if(x < 0 || x > *matrix width* - 1) return false;
if(y < 0 || y > *matrix height* -1) return false;
if (Map[x,y] == 1) return true;
return false;
}
and use it insead of the line tiles.Map[(int)playerPosition.X/60,(int)playerPosition.Y/60]
Or, if you need the type of tile returned
public int CollidesWithWall(int x, int y)
{
if(x < 0 || x > *matrix width* - 1) return -1;
if(y < 0 || y > *matrix height* -1) return -1;
return Map[x,y];
}
By doing it this way, you'll know if you stumbled upon a health potion (just set it's ID to like 3) or a wall (with ID of 1 or something, that's tottaly up to you) and if it is 0, it's empty space (or maybe -1). Notice that the "-1" part is totaly up to you. Just write down a list of id's that youll have and which items they present.
Other suggestions
Try if(tiles.Map[(int)(playerPosition.X/60f),(int)(playerPosition.Y/60f)] == 1)

XNA - 2D collision failure without any obvious pattern

Alright, so I am pretty new to XNA programming and I am trying to code a platformer. I have implemented pixel-perfect collision but it seems to fail for no apparent reason sometimes (I couldn't figure out a pattern) and the hero sprite goes through platforms.
static bool IntersectsPixel(Rectangle rect1, Color[] data1, Rectangle rect2, Color[] data2)
{
int top = Math.Max (rect1.Top, rect2.Top);
int bottom = Math.Min(rect1.Bottom, rect2.Bottom);
int left = Math.Max (rect1.Left,rect2.Left);
int right = Math.Min(rect1.Right,rect2.Right);
//Top
for(int y = top; y<bottom;y++)
for (int x = left; x < right; x++)
{
Color color1 = data1[x-rect1.Left + (y-rect1.Top) * rect1.Width];
Color color2 = data2[x - rect2.Left + (y - rect2.Top) * rect2.Width];
if (color1.A != 0 && color2.A != 0)
return true;
}
return false;
}
And here's the Update Method
protected override void Update(GameTime gameTime)
{
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
this.Exit();
foreach(Platform platform in platformList)
{
Rectangle check = new Rectangle(hero.GetRectangle().X - 300, hero.GetRectangle().Y - 300, 600, 600);
if(check.Intersects(platform.rectangle))
if (IntersectsPixel(hero.GetRectangle(), hero.textureData, platform.rectangle, platform.platformTextureData))
{
int direction = CheckDirection(platform,hero);
if (hero.hasJumped == true && direction == 3 && hero.velocity.Y <= 0 )
{
hero.velocity.Y = 0f;
hero.SetPosition(new Vector2((float)hero.GetPosition().X, (float)platform.rectangle.Bottom));
break;
}
else
if (direction == 4 && hero.velocity.X >= 0)
{
hero.velocity.X = 1;
hero.SetPosition(new Vector2((float)platform.rectangle.Left - (float)hero.GetRectangle().Width, (float)hero.GetPosition().Y));
break;
}
else
if (direction == 2 && hero.velocity.X <= 0)
{
hero.velocity.X = -1;
hero.SetPosition(new Vector2((float)platform.rectangle.Right - 1, (float)hero.GetPosition().Y));
break;
}
else
if (direction == 1 && hero.velocity.Y >= 0)
{
hero.velocity.Y = 0;
hero.hasJumped = false;
hero.SetPosition(new Vector2((float)hero.GetRectangle().X, (float)platform.rectangle.Y - (float)hero.GetRectangle().Height + 1));
hero.SetRectangle(new Rectangle((int)hero.GetPosition().X, (int)hero.GetPosition().Y, (int)hero.GetSize().X, (int)hero.GetSize().Y));
break;
}
}
}
hero.Update(gameTime);
camera.Update(gameTime, hero, screenBounds);
base.Update(gameTime);
}
And here's the direction check:
private int CheckDirection(Platform platform,Hero hero)
{
int distance = Math.Abs(platform.rectangle.Top - hero.GetRectangle().Bottom);
int direction = 1; //Top
if (distance > Math.Abs(platform.rectangle.Right - hero.GetRectangle().Left))
{
distance = Math.Abs(platform.rectangle.Right - hero.GetRectangle().Left);
direction = 2;
}
if (distance > Math.Abs(platform.rectangle.Bottom - hero.GetRectangle().Top))
{
distance = Math.Abs(platform.rectangle.Bottom - hero.GetRectangle().Top);
direction = 3;
}
if (distance > Math.Abs(platform.rectangle.Left - hero.GetRectangle().Right))
{
direction = 4;
distance = Math.Abs(platform.rectangle.Left - hero.GetRectangle().Right);
}
return direction;
}
Those are all my functions related to collision detection. If you happen to have any ideea of what might cause this, please let me know.
Thank you very much !

One thing I see that might be a possible reason is that right in the beginning where you build a box around both objects:
int top = Math.Max (rect1.Top, rect2.Top);
int bottom = Math.Min(rect1.Bottom, rect2.Bottom);
int left = Math.Max (rect1.Left,rect2.Left);
int right = Math.Min(rect1.Right,rect2.Right);
Unless you flipped it, typically XNA's Y grows positive as you go down (not up). This means you would actually want to take the Max of Bottom, and the Min of Top, since Top will always be less than Bottom. It looks like you already knew that though by the look of this line:
for(int y = top; y<bottom;y++)
I'll keep looking (it's difficult to test without the actual project). Another recommendation I'd give you is to do some debug drawing. Draw where the intersection functions thinks that pixels are touching or not touching.

Because of lag, Your character could be moving more than the blocks height per frame, so the collision may think it is in between blocks, and cause it to fly through.
https://gamedev.stackexchange.com/questions/30458/platformer-starter-kit-collision-issues
Check that out, It solved the problem for me.
Either slowing down movement, or clamping the change in position to the size of a block should solve this.

How to make monster move left then right continuously C# XNA

i'm making my first game on XNA for my class. I'm trying to make the monsters move left and right automatically. I have total 4 monsters for now. I'm trying to get them move left then right within the screen.
//Monster movements
for (int i = 0; i < numOfMonster; i++)
{
if (destinationMonster[i].X >= screenWidth - 60)
{
while(destinationMonster[i].X != -10)
moveLeft = true;
}
else
{
moveRight = true;
}
if (moveLeft)
{
int temp = destinationMonster[i].X;
temp = destinationMonster[i].X - monsterSpeed;
//This prevents the object passing the screen boundary
if (!(temp < -10))
{
destinationMonster[i].X = temp;
}
moveLeft = false;
}
if (moveRight)
{
int temp = destinationMonster[i].X;
temp = destinationMonster[i].X + monsterSpeed;
//This prevents the object passing the screen boundary
if (!(temp > screenWidth - 50))
{
destinationMonster[i].X = temp;
}
moveRight = false;
}
}

Your first problem is your while statement, once you enter it you are not going to exit because you are not changing your X value. If it were me I would have a bool array variable corresponding to each of your monsters. I would also change your conditional to trigger the change of the boolean value once the monster has reached the extents at either end. Something like this.
if (destinationMonster[i].X >= screenWidth - 60)
{
moveRight[i] = false ;
}
else if (destinationMonster[i].X <= -10)
{
moveRight[i] = true ;
}