I have written the code for if else if block but I want nested if else if loop like
If (flag)
If (c1) then
c2
Else
If (c3) then
c4
\documentclass{article}
\usepackage[ruled, lined, commentsnumbered, longend]{algorithm2e}
\begin{document}
\begin{algorithm}
\If{(flag)}{
\uIf{c1\;}{c2\;}
\uElse{
\uIf{c3\;}
{ c4\;}
}}
\end{algorithm}
\end{document}
Don't add extra line ends (\;) within the conditions. And you can use \uIf and/or \uElse to remove the closure.
The following achieves what you're looking for:
\documentclass{article}
\usepackage[ruled, lined, commentsnumbered, longend]{algorithm2e}
\begin{document}
\begin{algorithm}
\uIf{(flag)}{
\uIf{(c1)}{
c2
}
\uElse{
\uIf{(c3)}{
c4
}
}}
\end{algorithm}
\end{document}
I suggest you use algpseudocodex package.
\documentclass{article}
\usepackage{algorithm}
\usepackage{algpseudocodex}
\begin{document}
\begin{algorithm}
\caption{algorithm}
\label{alg}
\begin{algorithmic}[1]
\If{$a=b$}
\If{$a=b$}
\State $a=b$
\ElsIf{$a=b$}
\State $a=b$
\Else
\State $a=b$
\EndIf
\Else
\State $a=b$
\EndIf
\end{algorithmic}
\end{algorithm}
\end{document}
