## Thursday, August 11, 2016

### [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+^*```

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