a) 74
b) -18
c) 22
d) 40
- Postfix notation evaluates expressions by processing operands first, followed by operators.
Given expression: 6 3 2 4 + – *
- Scan the expression from left to right:
- 6, 3, 2, 4: These are operands, so we push them onto a stack.
- +: We encounter an operator. Pop the top two elements from the stack (4 and 2), add them (4 + 2 = 6), and push the result (6) back onto the stack.
- -: We encounter another operator. Pop the top two elements from the stack (6 and 3), subtract them (3 – 6 = -3), and push the result (-3) back onto the stack.
- *: We encounter the last operator. Pop the top two elements from the stack (6 and -3), multiply them (6 * -3 = -18), and push the result (-18) back onto the stack.
- Since we’ve reached the end of the expression, the final result is the only element left on the stack, which is -18.
Therefore, the value of the postfix expression 6 3 2 4 + – * is -18.