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Interview Question

Software Development Engineer Interview



Programming question - Given reverse polish notation, return the integer value of the expression aka "5,3,+,2,/" would be 5 + 3 = 8 and then 8 / 2 = 4.

Interview Answer

1 Answer


Use a stack. Push values onto the stack. When the token is an operator, pop the 2 values from the stack and apply the operator, pushing the result back onto the stack. Make sure to put the values on the correct sides of the operator. At the end, if it's a valid postfix notation or "reverse polish notation", there will be a single value on the stack. That's the answer. This notation is neat because there's no ambiguity, no need for parentheses.

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