# Basic CS-Data Structures [3i Infotech Placement]: Sample Questions 7 - 8 of 52

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## Question 7

Data Structures

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### Describe in Detail

Essay▾What are the notations used in Evaluation of Arithmetic Expression using prefix and postfix forms?

### Explanation

- Polish and reverse polish are the notations used in evaluation of arithmetic expression using prefix and postfix forms.

## Polish Notation

- Polish notation is also called as prefix notation.
- A form of notation for logic, arithmetic, and algebra.
- Its distinguishing feature is that it places operators to the left of their operands.
- While prefixing the operator to the number, it is called polish notation.
For example, ( (a + B) ⚹ C (D E) ^ (F + G) )

Prefix notation: ^ -⚹ + ABC-DE + FG

## Reverse Polish Notation

- A mathematical notation where every operator follows all of its operands, in contrast to Polish notation, which puts the operator in the prefix position.
- It suffixes the operator to the number called reverse polish notation.

Ex. . ( (a + B) ⚹ C (D E) ^ (F + G) )

Postfix notation: AB + C ⚹ DE — FG + ^

## Question 8

Data Structures

### Explanation

- Bubble sort is a good simple algorithm.
- Not suitable for large data sets as its average and worst-case complexity are of where n is the number of items.
- Beautiful algorithm easy to visualize with sorted elements bubbling up.

Bubble sort:

- let՚s solve unsorted array:

- 1
^{st}Iteration: - Start with two elements, comparing them to check which one is greater.

- Value 33 is greater than 14
- Therefore, they are in sorted locations.
- We compare 33 with 27.

- New array looks like

- Compare 33 and 35.
- Both are in sorted positions.

- The next two values, 35 and 10

- 10 is smaller then 35 and hence are not sorted.

- Swap values.
- We find that we reached the end of the array.

- We are showing how an array should looks like each iteration. One iteration brought 35 to its correct location it bubbled to the top
- After the second iteration.

- After each iteration, one value moves to correct position.

- When no swap is required, bubble sort learns that array is completely sorted.