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package DataStructures.Stacks;
import java.util.Stack;
public class InfixToPostfix {
public static void main(String[] args) throws Exception {
assert "32+".equals(infix2PostFix("3+2"));
assert "123++".equals(infix2PostFix("1+(2+3)"));
assert "34+5*6-".equals(infix2PostFix("(3+4)*5-6"));
}
public static String infix2PostFix(String infixExpression) throws Exception {
if (!BalancedBrackets.isBalanced(infixExpression)) {
throw new Exception("invalid expression");
}
StringBuilder output = new StringBuilder();
Stack stack = new Stack();
for (char element : infixExpression.toCharArray()) {
if (Character.isLetterOrDigit(element)) {
output.append(element);
} else if (element == '(') {
stack.push(element);
} else if (element == ')') {
while (!stack.isEmpty() && stack.peek() != '(') {
output.append(stack.pop());
}
stack.pop();
} else {
while (!stack.isEmpty() && precedence(element)