CareerCup

String toPostfix(String infixStr){
		
	if( infixStr == null ){
		throw new IllegalArgumentException("NULL str passed");
	}
		
	final StringBuilder postfixBuf = new StringBuilder( infixStr.length() );		
	final Deque<Character> operatorsStack = new LinkedList<Character>();
		
	for( char ch : infixStr.toCharArray() ){			
				
		// operator found				
		if( isOperator(ch) ){		
					
			while( ! operatorsStack.isEmpty() ){	
					
				char prevOperator = operatorsStack.pop();							
					
				if( compareOperators(prevOperator, ch ) < 0 ){
					operatorsStack.push(prevOperator);
					break;
				}
					
				postfixBuf.append( prevOperator );
			}
			
			operatorsStack.push(ch);
		}			
		// operand found
		else{
			postfixBuf.append( ch );
		}
	}
	
	while( ! operatorsStack.isEmpty() ){
		postfixBuf.append( operatorsStack.pop() );
	}
		
	return postfixBuf.toString();
}

@m}@{ algo & explnation plz..plz plz

make use of shuntington algorithm.
you see a operand you pass it to output.
you see a operator:
check the priority of operator on top of stack:
if higher priority push it to the stack
else (lower or equal priority) pop the operators until the one with lower priority is found
repeat till the end of the infix expression.

http :// scriptasylum . com/ tutorials/ infix_postfix/ algorithms/ infix-postfix/ index. htm

Hi there,
I gave amazon's written test for SDE, had similar exp. There were 3 questions I gave best solutions for 2 , still couldn't qualify. I doubt they look for solution which they already know. This is embarrassing!