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Evaluation of a Postfix Expression Question
1. For the given expression tree, write the correct postfix expression.
2. Which of the following is an example for a postfix expression?
3. Reverse Polish Notation is the reverse of a Polish Notation.
4. What is the time complexity of evaluation of postfix expression algorithm?
a) O (N)
b) O (N log N)
c) O (N2)
d) O (M log N)
Answer: O (N)
5. In Postfix expressions, the operators come after the operands.
6. Which of these operators have the highest order of precedence?
a) ‘(‘ and ‘)’
b) ‘*’ and ‘/’
c) ‘~’ and ‘^’
d) ‘+’ and ‘-‘
Answer: ‘~’ and ‘^’
7. Which of the following is not an application of stack?
a) evaluation of postfix expression
b) conversion of infix to postfix expression
c) balancing symbols
d) line at ticket counter
Answer: line at ticket counter
8. While evaluating a postfix expression, when an operator is encountered, what is the correct operation to be performed?
a) push it directly on to the stack
b) pop 2 operands, evaluate them and push the result on to the stack
c) pop the entire stack
d) ignore the operator
Answer: pop 2 operands, evaluate them and push the result on to the stack
9. Which of the following statement is incorrect?
a) Postfix operators use value to their right
b) Postfix operators use value to their left
c) Prefix operators use value to their right
d) In postfix expression, operands are followed by operators
Answer: Postfix operators use value to their right
10. What is the result of the given postfix expression? abc*+ where a=1, b=2, c=3.
11. What is the result of the following postfix expression?
ab*cd*+ where a=2,b=2,c=3,d=4.
12. Consider the stack
| 5 |
| 4 |
| 3 |
| 2 |.
At this point, ‘*’ is encountered. What has to be done?
a) 5*4=20 is pushed into the stack
b) * is pushed into the stack
c) 2*3=6 is pushed into the stack
d) * is ignored
Answer: 5*4=20 is pushed into the stack
13. Evaluate the postfix expression ab + cd/- where a=5, b=4, c=9, d=3.
14. Evaluate and write the result for the following postfix expression
abc*+de*f+g*+ where a=1, b=2, c=3, d=4, e=5, f=6, g=2.
15. What is the other name for a postfix expression?
a) Normal polish Notation
b) Reverse polish Notation
c) Warsaw notation
d) Infix notation
Answer: Reverse polish Notation
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