[SPOJ] ONP – Transform the Expression

http://www.chenguanghe.com/category/spoj/
http://www.spoj.com/problems/ONP/

Transform the algebraic expression with brackets into RPN form (Reverse Polish Notation). Two-argument operators: +, -, *, /, ^ (priority from the lowest to the highest), brackets ( ). Operands: only letters: a,b,...,z. Assume that there is only one RPN form (no expressions like a*b*c).

Input

t [the number of expressions <= 100]
expression [length <= 400]
[other expressions]

Text grouped in [ ] does not appear in the input file.

Output

The expressions in RPN form, one per line.

Example

Input:
3
(a+(b*c))
((a+b)*(z+x))
((a+t)*((b+(a+c))^(c+d)))

Output:
abc*+
ab+zx+*
at+bac++cd+^*

一个代数表达式转换成Reverse Polish Notation. 分析: wiki上就有规则. 其实这个题只有三个规则: 看到(, 忽略 看到操作符(加减乘除)入栈 看到), 出栈,打印 其余直接打印

    public void solve(int testNumber, InputReader in, OutputWriter out) {

        String s = in.readLine();

        out.printLine(infixToPostfix(s));

    }

    public String infixToPostfix(String infix) {

        Stack<Character> st = new Stack<>();

        StringBuffer sb = new StringBuffer();

        String opt = "+-*/^";

        for (int i = 0; i < infix.length(); i++) {

            Character c = infix.charAt(i);

            if (c.equals('('))

                continue;

            else if (opt.contains(c.toString()))

                st.push(c);

            else if (c.equals(')'))

                sb.append(st.pop());

            else

                sb.append(c);

        }

        return sb.toString();

    }