Rajasthan Computer Teacher Preparation – Day 1: DSA

Rajasthan Computer Teacher Preparation – Day 1: DSA with Examples & MCQs

If you’re starting your Rajasthan Computer Teacher exam preparation, Day 1 should focus on DSA (Data Structures & Algorithms), especially arrays and time complexity. This guide is simple, with examples and MCQs to make practice easy.

Step 1: Time Complexity – 15 Minutes

Time complexity tells you how fast your code runs. Many mistakes happen here, so review it first.

Key Complexities

Complexity	Example	Quick Tip
O(1)	arr[0] – Access first element	Instant access
O(n)	Sum of all elements in array	Loop through each element
O(n log n)	MergeSort	Efficient for large arrays
O(n²)	Nested loops like bubble sort	Avoid for big inputs

Example:

# Find sum of array elements
arr = [1,2,3,4,5]
total = 0
for num in arr:   # O(n)
    total += num
print(total)      # Output: 15

Quick MCQs on Time Complexity

1. Accessing an element in an array has time complexity:
a) O(1)
b) O(n)
c) O(n²)
Answer: a) O(1)

2. Bubble sort worst-case complexity is:
a) O(n)
b) O(n log n)
c) O(n²)
Answer: c) O(n²)

3. Sum of all elements in an array of size n:
a) O(n)
b) O(1)
c) O(n²)
Answer: a) O(n)

Step 2: Arrays Practice – 30 Minutes

Instead of random problems, focus on 10 high-value questions. Here are examples and patterns:

1. Max/Min in Array

arr = [4, 2, 9, 7]
max_val = max(arr)  # 9
min_val = min(arr)  # 2

Max element in [3, 8, 1, 6]?
a) 3
b) 6
c) 8
Answer: c) 8

2. Prefix Sum

arr = [1,2,3,4]
prefix_sum = [0]*len(arr)
prefix_sum[0] = arr[0]
for i in range(1, len(arr)):
    prefix_sum[i] = prefix_sum[i-1] + arr[i]
print(prefix_sum)  # Output: [1,3,6,10]

Prefix sum of [2,4,6]?
a) [2,6,12]
b) [2,4,6]
c) [2,6,10]
Answer: a) [2,6,12]

3. Two Pointers

arr = [1,2,3,7,8]
arr.sort()
i, j = 0, len(arr)-1
while i < j:
    if arr[i] + arr[j] == 10:
        print(arr[i], arr[j])  # Output: 2 8
        break
    elif arr[i] + arr[j] < 10:
        i += 1
    else:
        j -= 1

Pair with sum 7 in [1,3,4,5]?
a) 1,4
b) 3,5
c) 2,5
Answer: b) 3,4

4. Rotate Array

arr = [1,2,3,4,5]
k = 2
rotated = arr[-k:] + arr[:-k]
print(rotated)  # Output: [4,5,1,2,3]

Right rotate [1,2,3] by 1 → ?
a) [1,2,3]
b) [3,1,2]
c) [2,3,1]
Answer: b) [3,1,2]

5. Search for an Element

# Linear search example
arr = [2,4,7,8]
target = 7
for i in range(len(arr)):
    if arr[i] == target:
        print("Found at index", i)  # Output: Found at index 2
        break

Linear search for 7 in [2,4,7,8] → Index?
a) 0
b) 2
c) 3
Answer: b) 2

6. Reverse Array

arr = [1,2,3,4]
arr.reverse()
print(arr)  # Output: [4,3,2,1]

Reverse [5,6,7] → ?
a) [5,6,7]
b) [7,6,5]
c) [6,7,5]
Answer: b) [7,6,5]

7. Merge Two Arrays

a = [1,3,5]
b = [2,4,6]
merged = sorted(a + b)
print(merged)  # Output: [1,2,3,4,5,6]

Merge [1,2] and [3,0] → ?
a) [0,1,2,3]
b) [1,2,3,0]
c) [3,0,1,2]
Answer: a) [0,1,2,3]

Wrap-Up

Day 1 Plan Summary:

15 min → Time Complexity Review
30 min → 7 Patterns of Array Problems
Solve high-quality examples, not random questions
Practice MCQs to strengthen concepts

Follow this plan and start your Rajasthan Computer Teacher exam prep confidently!