Solving a wordsearch puzzle in matlab - matlab

Question

Posting the entirety of my code in the hope somebody can help me debug this crap. Really hoping to reach a conclusion soon because I've been toying with this for way too long.
I have here a function extract which is passed a grid of integers which represent letters (i.e A=1,Z=26) from my wordsearch function. Given a direction and a target word which is represented by a row vector of ints, it should iterate through the grid to find where the first letter exists and move in all directions from here for length of the word and extract the word e.g. if we are looking for [14, 5, 9, 2] and 14 is first positioned at (4,4) we should end up at (4,8).
The word is then compared in the search function and if it matches the target word, a line is drawn from first letter to the last on an image of the actual wordsearch.
I know my if and for loops are off in some places but I'm finding it difficult to correct my code so that it works. Help! One thing in particular I'm having difficulty with is controlling flow so that if after checking all directions from a square containing the first letter, the next instance of that letter is evaluated. Where would it be best to do this?
Code has lots of errors as it is and could do with a couple of pointers telling me where it needs altering or cleaning up.
%//A function to find a word in a grid.
function test = extract(grid, direction, target)
%//switch through different cases that allow us to move to any adjacent cell to the current
switch upper(direction)
case 1
rowdir = -1;
coldir = 0;
case 2
rowdir = -1;
coldir = 1;
case 3
rowdir = 0;
coldir = 1;
case 4
rowdir = 1;
coldir = 1;
case 5
rowdir = 1;
coldir = 0;
case 6
rowdir = 1;
coldir = -1;
case 7
rowdir = 0;
coldir = -1;
case 8
rowdir = -1;
coldir = -1;
end
[i, j] = size(grid);
len = length(target);
[row,column] = find(target(1)==grid); %//find the letter of the word we are looking for in grid
%//row and column of last letter having moved in a particular direction
rowN = row + (len-1) * rowdir;
colN = column + (len-1) * coldir;
%//trying to say here to only move in a particular direction if we don't go out of bounds.
%//not sure I've succeeded
if (rowN > 1) | (rowN < i) | (colN > 1) | (colN < j)
testword = []; %empty array created
for index = 1:len
index_1 = index-1;
%//on loop get the letter in adjacent cell for direction we have moved
word = grid(row + (index_1 * rowdir), column + (index_1 * coldir));
testword{index} = word; %//letters are appended to create word for which we compare.
%//get co-ords of start letter. change to pixel co-ordinates so we can evaluate on image
wordstart = [(row*30)-15, (column*30)-15 ];
wordend = [((row + (len-1 * rowdir))*30)-15, ((column + (len-1 * coldir))*30)-15];
end
else
word = '';
end
x1 = wordstart(1);
x2 = wordend(1);
y1 = wordstart(2);
y2 = wordend(2);
test = [ word , [x1,x2] , [y1,y2]]; %//only way I could think of to get all of these as outputs
end
%//test is the image we want to evaluate on
%//words is the list of words
function trial1 = wordsearch(test, words)
imagesc(test);
colormap(gray);
hold on;
grid = %//grid is a 15x15 matrix
[row, column] = size(grid);
for iword = 1 : length(words)
target = char(words(iword)) - 'a' + 1;
for i = 1:row
for j = 1:column
for direction_num = 1:8 %//for each direction
direction = directions(direction_num, :);
testword = extract(grid,direction,target);
if testword(1)==target %//if word we have extracted equals the target word
%//draw_line function takes x co-ordinates and y co-ordinates and plots line.
draw_line(testword(2),testword(3),testword(4),testword(5));
end
end
end
end
end
hold off;
end
#Dan
My extract function now looks like:
[i, j] = size(grid);
len = length(target);
[row,column] = find(target(1)==grid);
for ii = 1:length(row)
start_row = row(ii);
start_column = column(ii);
rowN = start_row + len-1 * rowdir;
colN = start_column + len-1 * coldir;
if (rowN > 1) || (rowN < i) || (colN > 1) || (colN < j)
testword = [];
for index = 1:len
index_1 = index-1;
word = grid(start_row + (index_1 * rowdir), start_column + (index_1 * coldir));
testword{index} = word;
wordstart = [(start_row*30)-15, (start_column*30)-15 ];
wordend = [((start_row + (len-1 * rowdir))*30)-15, ((start_column + (len-1 * coldir))*30)-15];
end
else
end
end
What would I put as an else statement to check the word if previous in that particular direction takes you out of bounds?

Answer 1

for iword = 1 : length(words)
target = char(words(iword)) - 'a' + 1;
for i = 1:row
for j = 1:column
for direction_num = 1:8 %//for each direction
For every word, you are looping through every element in the grid (i.e. the i and j loops) but you don't actually ever use these i or j values. So those two loops do nothing! This is because you seems to do all of that inside your extract function. So drop those two loops, they are wasting an inordinate amount of time.
Inside your extract function, you have a line [row,column] = find.... This will find ALL the possible starting points. So you actually need to loop through either of those somewhere. So instead of your if (rowN > 1) | (rowN < i) | (colN > 1) | (colN < j) I would suggest something more like:
for ii = 1:length(row)
start_row = row(ii);
start_column = column(ii);
%// And now re-use your code, but swap out all your row for start_row and your column for start_column
.
.
.
end
That is the loop that will go through each of the possible starting letters.