How to store the number of iterations used until the while loop condition is met?

I am coding a 2D collision problem in a 11x11 grid. In my while loop, I am trying to code that when an if condition of both particles A and B share the same coordinates, the number of steps used until this condition is met gets stored in the Moves array and it doesn't work the way I want it as 0, 1, and 2 gets stored in the Moves array and that's IMPOSSIBLE since it's a 11x11 grid and A & B can't just move 1, 2, or no steps until they meet knowing that they are allowed to move randomly in any direction one tile pers step. Here's my code so far.

I STILL NEED HELP!

for j = 1:5000
            % run while loop if Collision is not found.
            Collision = 0; k = 0;
            while Collision == 0 && k < 1000
                  k = k + 1;
                  % Using the RandWalk_2D function for the new position of A and B.
                  [xAkp1, yAkp1] = RandWalk_2D(xAk,yAk,BC);
                  [xBkp1, yBkp1] = RandWalk_2D(xBk,yBk,BC);
                  % Create the path of particle A.
                  xAkPATH = [xAk - 0.5, xAk + 0.5, xAk + 0.5, xAk - 0.5];
                  yAkPATH = [yAk - 0.5, yAk - 0.5, yAk + 0.5, yAk + 0.5];
                  xAkp1PATH = [xAkp1 - 0.5, xAkp1 + 0.5, xAkp1 + 0.5, xAkp1 - 0.5];
                  yAkp1PATH = [yAkp1 - 0.5, yAkp1 - 0.5, yAkp1 + 0.5, yAkp1 + 0.5];
                  % Create the path of particle B.
                  xBkPATH = [xBk - 0.5, xBk + 0.5, xBk + 0.5, xBk - 0.5];
                  yBkPATH = [yBk - 0.5, yBk - 0.5, yBk + 0.5, yBk + 0.5];
                  xBkp1PATH = [xBkp1 - 0.5, xBkp1 + 0.5, xBkp1 + 0.5, xBkp1 - 0.5];
                  yBkp1PATH = [yBkp1 - 0.5, yBkp1 - 0.5, yBkp1 + 0.5, yBkp1 + 0.5];
                  % Update new positions of A and B.
                  xAk = xAkp1; yAk = yAkp1;
                  xBk = xBkp1; yBk = yBkp1;
                  % if condition when both A and B collide to restart a new trial.
                  if xAk == xBk && yAk == yBk
                     % Collision happens! 
                     Collision = 1;
                     % Storing the number of moves in this trial in the 'Moves' array.
                     Moves(j) = k;
                  end
            end
end            

[Jackson Burns]

Your code seems fine to me, but I can'tbe sure without seeing:

RandWalk_2D

I suspect the error is in there.

[Mina Mansour]

Here is the function RandWalk_2D

function [x, y] = RandWalk_2D(x0, y0, BC)
% Function (RandWalk_2D)
% This function gives the ability for the particle to move randomly in all direction on the grid.
% There are five posibilities either upwards, downwards, left, right, or stay still.
% When at the boundries, the particle cannot pass one of them, but instead it forfeits it's turn.

    % Setting a random number for movement.
    r = rand;
    % Moving upwards.
    if r <= 0.2
        x = x0; y = y0 + 1;
        if y >= BC(1)
            y = BC(1);
        end
    % Moving to the right.    
    elseif 0.2 < r && r <= 0.4
        x = x0 + 1; y = y0;
        if x >= BC(2)
            x = BC(2);
        end
    % Moving downwards. 
    elseif 0.4 < r && r <= 0.6
        x = x0; y = y0 - 1;
        if y <= BC(3)
            y = BC(3);
        end
    % Moving to the left.
    elseif 0.6 < r && r <= 0.8
        x = x0 - 1; y = y0;
        if x <= BC(4)
            x = BC(4);
        end
    % Staying in position.
    elseif 0.8 < r && r < 1
        x = x0; y = y0;
    end
end