Sure, here is a step-by-step guide on how to evaluate a postfix expression using a stack in Python:

1. Initialize an empty stack.

2. Scan the postfix expression from left to right.

3. If the scanned character is a digit, push it into the stack.

4. If the scanned character is an operator, pop two elements from the stack, apply the operator, and push the result back to the stack.

5. Repeat steps 3 and 4 until the expression is scanned completely.

6. The final result will be in the stack.

Here is a Python function that implements the above steps:

```python
def evaluate_postfix(expression):
stack = []
for char in expression:
if char.isdigit():
stack.append(int(char))
else:
val1 = stack.pop()
val2 = stack.pop()
switcher = {
'+': val2 + val1,
'-': val2 - val1,
'*': val2 * val1,
'/': val2 / val1
}
stack.append(switcher.get(char))
return stack[0]

print(evaluate_postfix("94*2/"))
```

This function will output `18` for the input `"94*2/"`, which is the correct result.

Question

Sure, here is a step-by-step guide on how to evaluate a postfix expression using a stack in Python:

1. Initialize an empty stack.

2. Scan the postfix expression from left to right.

3. If the scanned character is a digit, push it into the stack.

4. If the scanned character is an operator, pop two elements from the stack, apply the operator, and push the result back to the stack.

5. Repeat steps 3 and 4 until the expression is scanned completely.

6. The final result will be in the stack.

Here is a Python function that implements the above steps:

```python
def evaluate_postfix(expression):
    stack = []
    for char in expression:
        if char.isdigit():
            stack.append(int(char))
        else:
            val1 = stack.pop()
            val2 = stack.pop()
            switcher = {
                '+': val2 + val1,
                '-': val2 - val1,
                '*': val2 * val1,
                '/': val2 / val1
            }
            stack.append(switcher.get(char))
    return stack[0]

print(evaluate_postfix("94*2/"))
```

This function will output `18` for the input `"94*2/"`, which is the correct result.

Knowee AI · Accepted Answer