MATLAB – Read Words in a File in Reverse Order

MATLAB stands for Matrix Laboratory. It is a high-performance language that is used for technical computing. It allows matrix manipulations, plotting of functions, implementation of algorithms, and creation of user interfaces

Suppose we are given a text file containing the following words “I STUDY FROM GEEKS FOR GEEKS”. Now, if we want to read the words of the file in the reverse order, the outcome should be “GEEKS FOR GEEKS FROM STUDY I”.

Algorithm:

• Open the given file using fopen() function (This function takes the name of the file as its argument and returns a pointer to a FILE structure type that can be used to access the open file).
• Jump the returned pointer to the end of the given text file using fseek() function
• Now, shift that pointer to the end-1 position.
• Read the character to which the pointer is pointing using fread() function and store it in a matrix.
• Next, shift the pointer to the current-2 position, again read the character to which the pointer is pointing, and store it in a matrix.
• Now, If the character is a blank space, then reverse the array.  Use fliplr() to reverse the array/
• Then,  append the array to a string and initialize the array to zero.
• Replicate this algorithm till the pointer fp reaches the starting of the file.
• Close the file using fclose() function.

Example 1: 

Matlab

% MATLAB program for read words
% Opening the given file to read,
% name of the file is passed as
% an argument in fopen() function.
fp=fopen('rev.txt');

% Using fseek(),
% we will move fp to the end of file.
fseek(fp,0,'eof');

% Finding the position of fp using ftell()
fsz=ftell(fp);
i=1;

% Using fseek(), move fp to
% the current-1 position.
fseek(fp,-1,'cof');

% Using fread(),read a character
chr=fread(fp,1,'*char');

% Store the character in the matrix Z.
Z(1,i)=chr;
Word=0;

% Checking if fp has reached to
% start of the file.
    while(fseek(fp,-2,'cof')~=-1)

        c=fread(fp,1,'*char');
        % Character array is
        % reversed and appended into a string when a space occurs.
        if(isspace(chr))
              if(Word==0)
                  %Step 9- At first, the string is empty.
                  % Step 10- Now, the array is appended in
                  % the reverse order with a blank space.
                   Word=[fliplr(Z) blanks(1)];
              else
                  % Append the reversed character
                  % array to the string
                   Word=[Words fliplr(Z)];
              end
           i=1;
           Z='';
        else
            % The array is updated with the
            % characters until blank space is
            % encountered
           i=i+1;
           Z(1,i)=chr;

        end


    end

Word=[Word fliplr(Z)];
display(Word);

fclose(fp);

Output: