Stack algorithms of pop operation

Stack algorithms:

This algorithm is for deletion of an element from stack:

1) if( top == NULL)

a) print“Stack is empty”

b) return

2) temp = top

3) num = temp→data

4) top = top→link

5) delete temp

6) return num

7) Exit

This algorithm is for evaluation of postfix expression:

Description: Here P is a postfix expression and this algorithm evaluates it.

1. Add a “)” right parenthesis at the end of P.

2. Scan P from left to right and repeat steps 3 & 4 for each element

Of P until “)” is encountered.

3. If an operand is encountered, push it onto stack.

4. If an operator U is encountered then:

(a) Pop the top two elements from stack, where A is the

Top element and B is the next to top element.

(b) Evaluate B U A.

[End of Step 4 If]

[End of step 2 For Loop]

5. Set VALUE equal to the top element on the stack.

6. Exit.