1、首先引入几个需要用到的包
\usepackage{algorithm} %format of the algorithm
\usepackage{algorithmic} %format of the algorithm
\usepackage{multirow} %multirow for format of table
\usepackage{amsmath}
\usepackage{xcolor}
2、重新定义require和ensure命令对应的关键字(此处将默认的Require/Ensure自定义为Input/Output)
3、\renewcommand{\algorithmicrequire}{\textbf{Input:}}
\renewcommand{\algorithmicensure}{\textbf{Output:}}
4、分析一下示例：
\begin{algorithm} %算法开始
\caption{Sample algorithm} %算法的题目
\label{alg1} %算法的标签
\begin{algorithmic}[1] %此处的[1]控制一下算法中的每句前面都有标号
\REQUIRE Text:Today is a good day. Variables:$u,v,w$. $G=(V,E)$ %输入条件(此处的REQUIRE默认关键字为Require，在上面已自定义为Input)
5、\ENSURE Something... %输出结果(此处的ENSURE默认关键字为Ensure在上面已自定义为Output)
% if-then-else
\IF{some condition is true}
\STATE do some processing
\ELSIF{some other condition is true}
\STATE do some different processing
\ELSE
\STATE do the default actions
\ENDIF
% for loop
\FOR{$i=0$ to $10$}
\STATE carry out some processing
6、\ENDFOR
\FORALL{$i$ such that $0\leq i\leq 10$}
\STATE carry out some processing
\ENDFOR
% while-loop
\WHILE{some condition holds}
\STATE carry out some processing
\ENDWHILE
% repeat-until loop
\REPEAT
\STATE carry out some processing
\UNTIL{some condition is met}
% infinite loop
\LOOP
\STATE this processing will be repeated forever
\ENDLOOP
\end{algorithmic}
\end{algorithm}
