Evaluate a postfix expression
Postfix expression: Operand1 Operand2 op1
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12While (we have not reached the end of s)
If an operand is found
Push it onto the stack
End-If
If an operator is found
Pop the stack and call the value B
Pop the stack and call the value A
Evaluate A op B using the operator just found
Push the result onto the stack
End-If
End-While
Pop the stack (this is the final value)
Evaluate a infix expression
Infix expression: Operand1 op Operand21
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24Stacks: ops, values
While (we have not reached the end of s)
If an operand is found
Push it onto the stack: values
End-If
If a left parenthesis is found
Push it onto the stack: ops
End-If
If a right parenthesis is found
While (the stack: ops is not empty AND the top item is not a left parenthesis)
Pop the stack: ops and add the popped value to stack: values
End-If
If an operator is found
While (the stack is not empty AND the top of the stack is not a left parenthesis AND precedence of the operator <= precedence of the top of the stack)
Pop the stack: ops and add the top value to stack: values
End-While
Push the latest operator onto the stack: ops
End-If
End-While
While (the stack is not empty)
Pop the stack and add the popped value to stack: values;
End-While
Pop the stack (this is the final value)