Answers and Solutions

Answer

C . 3

Answer

C . 3

Answer

C) 3

Applying the postfix expression evaluation.

Following is algorithm for evaluation postfix expressions. 1) Create a stack to store operands (or values). 2) Scan the given expression and do following for every scanned element.

       a) If the element is a number, push it into the stack

       b) If the element is a operator, pop operands for the operator from stack. Evaluate the operator and push the result                 back to the stack

3) When the expression is ended, the number in the stack is the final answer

Let the given expression be “2 3 1 * + 9 -“. We scan all elements one by one. 1) Scan ‘2’, it’s a number, so push it to stack. Stack contains ‘2’ 2) Scan ‘3’, again a number, push it to stack, stack now contains ‘2 3’ (from bottom to top) 3) Scan ‘1’, again a number, push it to stack, stack now contains ‘2 3 1’ 4) Scan ‘*’, it’s an operator, pop two operands from stack, apply the * operator on operands, we get 3*1 which results in 3. We push the result ‘3’ to stack. Stack now becomes ‘2 3’. 5) Scan ‘+’, it’s an operator, pop two operands from stack, apply the + operator on operands, we get 3 + 2 which results in 5. We push the result ‘5’ to stack. Stack now becomes ‘5’. 6) Scan ‘9’, it’s a number, we push it to the stack. Stack now becomes ‘5 9’. 7) Scan ‘-‘, it’s an operator, pop two operands from stack, apply the – operator on operands, we get 5 – 9 which results in -4. We push the result ‘-4’ to stack. Stack now becomes ‘-4’. 8) There are no more elements to scan, we return the top element from stack (which is the only element left in stack)

Thnak You

Answer

Answer

C. 3

Answer

Option C is correct

Answer

Answer

3

Answer

3

Answer

3

Answer

3

Answer

3

Answer

The answer is 3.

Answer

• C

  3