CSE 214 Lecture Notes - Lecture 1: Reverse Polish Notation, Infix Notation, Operand
27 Jul 2017
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The operands precede the operator (@ means + - * or /) 3 4 + = 3+4= 7: in the expression, replace @ and its operands with the computed value, repeat 1-3 the process until no more operators exist. Here is the sequence of operations: 2 3 4 * , 2 12 + 3 4*is replaced by 12 , the value of 3*4. + is next operator, perform 2 12+ replace 2 12+ with 14. Another example, 3 4 * 2 5 * + which in infix notation is 3*4 + 2*5. * is the first operator 3 4 * is replaced by 12. 1: when you are finished scanning the expression, the final value remains on the stack. Pop 4, pop 3, do 3 *4 , push 12. Pop 12, pop 2, do 2 + 12, push 14. Here is an algorithm to evaluate postfix expressions. To eliminate some unnecessary and non-instructive details make a few simplifying assumptions:
