Not able to get proper for loop and if

Question

\usepackage{algorithm}
\usepackage{algpseudocode}

\begin{document}
\begin{algorithm}
\caption{Brute-Force algorithm}

\begin{algorithmic}[1]

\For {$s'$ \in ${\mathbb{F}^n_2}$}{
    \If {$wt(As'+b)$ \leq $t$}{
        return $s'$}
    }
\end{algorithmic}
\end{algorithm}
\end{document}

\end{onehalfspacing}

Just want to remove this extra part that is marked with red pen

Answer 1

If the following is the output you were looking for, then you forgot to close the If and For blocks. Also, there are some issues, with using \leftarrow instead of the packages \gets and some other minor issues with your way of using math mode:

\documentclass{scrartcl}

\usepackage{algorithm}
\usepackage{algpseudocode}
\usepackage{float}

\begin{document}
    \begin{minipage}{.6\linewidth}
        \begin{algorithm}[H]
            \caption{Brute-Force algorithm}
            \begin{algorithmic}[1]
                \State \textbf{Input:} dimension $d \in \mathbf{N}$, error rate $\tau \in \left[0,\frac{1}{2}\right)$
                \State \textbf{Output:} secret $\mathbf{s}$
                \State $n$ = $4d $(\( \frac{1}{2} \) - \(\tau\))$^{-2}$ ,
                \State $ (A,b) \gets Orc^n_{d,\tau} $
                \For {$s' \in \mathbf{F}^n_2$}
                    \If{$wt(As'+b) \leq t$}
                        return s'
                    \EndIf
                \EndFor
            \end{algorithmic}
        \end{algorithm}
    \end{minipage}
\end{document}