Algorithm in LaTeX

Question

I wrote the following algorithm, however its not compiling and throws a few errors. I am not sure of what I did wrong. Any help would be appreciated.

\begin{algorithm}
    \caption{Bridging Score(BRS) Computation}
    \begin{algorithmic}
     Given: User-Noun Matrix $X$
     \For {$i = 1 \to n$}
    Let $S_i$ = {$s{i,j}$ | $0\le j \le l_i$} be set of nodes which have links to $i$;
    \IF $\left({l_i=0$ OR $l_i=1 \right)}$ \THEN
      $b_i=0$;
    \ELSE
      Compute the similarity score vectors $r_{s,1},r_{s,2},...,r_{s,l_i}$ for each $S_i=s_1,s_2,...s_{l_i}$; \\
      Construct $l_i \times l_i$ matrix $R_i= \left[r_{s,1},r_{s,2},...,r_{s,l_i}\right]$;
      Take the average of all non-diagonal elements in $R_i$ to obtain $\hat{r_s}$;
      $b_i= 1/\hat{r_s}$;
      \ENDIF
 \ENDFOR
 \RETURN vector $b$ of bridging scores;
    \end{algorithmic}
\end{algorithm}

Answer 1

It is not completely clear to me which algorithm typesetting package are you using, since you did not include the document preamble, and your code is a strange jumble of several different syntaxes, mostly looking like the old algorithms package syntax, but not quite. Your tags seem to indicate that you are using the algorithmicx bundle, so I assume that you use the algpseudocode package. You need to correct some syntax, for example algpseudocode does noy capitalize command, only first letter, so you should have \If ... \Else ... \EndIf etc.

Also, command \For and \If take an argument, so you need

\If{something something}

The \If does not use \Then, you should leave that out.

Every line must have a command, so you should either define your own commands for things like "Given:", or just use \State.

The following will hopefully do what you expect it to do:

\documentclass{article}
\usepackage{algpseudocode}
\usepackage{algorithm}
\begin{document}
\begin{algorithm}
   \caption{Blah blah}
   \begin{algorithmic}[1]
      \State Given: User-Noun Matrix $X$
      \For{$i = 1 \to n$}
         \State Let $S_i$ = {$s{i,j}$ | $0\le j \le l_i$} be set of nodes which have links to $i$;
         \If{$\left(l_i=0 \hbox{OR} l_i=1 \right)$}
            \State $b_i=0$;
         \Else
            \State Compute the similarity score vectors $r_{s,1},r_{s,2},...,r_{s,l_i}$ for each $S_i=s_1,s_2,...s_{l_i}$; \\
            \State Construct $l_i \times l_i$ matrix $R_i= \left[r_{s,1},r_{s,2},...,r_{s,l_i}\right]$;
            \State Take the average of all non-diagonal elements in $R_i$ to obtain $\hat{r_s}$;
            \State $b_i= 1/\hat{r_s}$;
         \EndIf
      \EndFor
    \State \Return vector $b$ of bridging scores;
\end{algorithmic}
\end{algorithm}
\end{document}

The algorithmicx bundle have pretty good documentation with a number of examples, I suggest you take a look at it.