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Data Structure & Algorithm Interview Questions And Answers - Part X.

Here, are some sample questions based on "Data Structures". Read it carefully as these questions will help you in cracking any interview.

46) What do you mean by Polish string ?

Answer: Polish string refers to the notation in which the operator symbol is placed either before its operands (prefix notation) or after it operands (postfix notation). The usual form, in which the operator is placed in between the operands is called infix notation.

47) What do you mean by an infix, postfix and prefix expression ?

Answer: An expression where operators are placed in between the operands is called a infix expression.
E.g.: A + B

An expression where operators are placed after the operands is called a postfix expression.
E.g.: AB+

An expression where operators are placed before the operands is called a prefix expression.
E.g.: +AB

48) What is the evaluation order according to which an infix expression is converted to postfix expression ?

Answer: The evaluation order is:

I. Brackets or Parenthesis,
II. Exponentiation,
III. Multiplication or division,
IV. Addition or subtraction.

The operators with the same priority are evaluated from left to right.

49) Give the advantages of using post fix notations over infix notations ?

Answer: An infix expression is evaluated keeping in mind the precedence of operators. An infix expression is difficult for the machine to know and keep track of precedence of operators. A postfix expression itself takes care of the precedence of operators as the placement of operators. Thus, for the machine, it is easier to carry out a postfix expression than an infix expression.

50) How can prefix notations be converted to infix form ?

Answer: A prefix expression is converted to infix expression by scanning from left to right until we find the first operator that is immediately followed by a pair of operands. This binary expression is converted to infix by placing the operator in between two operands. The resultant expression continues until all the operators are placed between operands.


36) What are the differences between linear search and binary search ?
37) State the condition(s) under which binary search is applicable ?
38) What are the advantages of linked lists over arrays ?
39) What is sorting of an array ? Name a few types of sorting techniques ?
40) What is the mechanism of selection sort ?

41) What do you mean by bubble sort ?
42) What is insertion sort ?
43) Differentiate between the different types of linked lists ?
44) What do you mean by ‘pushing’ and ‘popping’ with regard to stacks ?
45) What are input restricted dequeues and output restricted dequeues ?

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