Data Structures & Algorithms for Competitive Exam Prep

Data Structures & Algorithms

Q. What is the purpose of the 'visited' array in Dijkstra's algorithm?

A. To store the shortest path
B. To track the vertices that have been processed
C. To store the distances from the source
D. To hold the edges of the graph

Solution

The 'visited' array in Dijkstra's algorithm is used to track which vertices have been processed to avoid reprocessing them.

Correct Answer: B — To track the vertices that have been processed

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Q. What is the result of a binary search if the array is empty?

A. Returns 0
B. Returns -1
C. Returns null
D. Returns an error

Solution

If the array is empty, binary search will return -1, indicating that the target is not found.

Correct Answer: B — Returns -1

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Q. What is the result of a level-order traversal of a binary tree?

A. Nodes are visited from top to bottom and left to right
B. Nodes are visited from bottom to top and right to left
C. Nodes are visited in sorted order
D. Nodes are visited in reverse order

Solution

Level-order traversal visits nodes level by level, starting from the root and moving from left to right.

Correct Answer: A — Nodes are visited from top to bottom and left to right

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Q. What is the result of a level-order traversal of the following binary tree: 1, 2, 3, 4, 5?

A. 1, 2, 3, 4, 5
B. 1, 3, 2, 5, 4
C. 2, 4, 3, 5, 1
D. 4, 5, 2, 3, 1

Solution

Level-order traversal visits nodes level by level from top to bottom, resulting in 1, 2, 3, 4, 5.

Correct Answer: A — 1, 2, 3, 4, 5

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Q. What is the result of a level-order traversal on a binary tree with root 1, left child 2, and right child 3?

A. 1, 2, 3
B. 2, 1, 3
C. 1, 3, 2
D. 3, 2, 1

Solution

In level-order traversal, we visit nodes level by level from top to bottom, resulting in the sequence 1, 2, 3.

Correct Answer: A — 1, 2, 3

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Q. What is the result of a level-order traversal on the binary tree with root 1, left child 2, and right child 3?

A. 1, 2, 3
B. 2, 1, 3
C. 3, 2, 1
D. 1, 3, 2

Solution

Level-order traversal visits nodes level by level, starting from the root, resulting in the order: 1, 2, 3.

Correct Answer: A — 1, 2, 3

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Q. What is the result of a post-order traversal of a binary tree?

A. Root, Left, Right
B. Left, Right, Root
C. Right, Left, Root
D. Left, Root, Right

Solution

In post-order traversal, the nodes are visited in the order: Left, Right, Root.

Correct Answer: B — Left, Right, Root

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Q. What is the result of a post-order traversal on a binary tree with nodes 1 (root), 2 (left), 3 (right)?

A. 1, 2, 3
B. 2, 3, 1
C. 3, 2, 1
D. 1, 3, 2

Solution

Post-order traversal visits the left child, then the right child, and finally the root, resulting in the output 2, 3, 1.

Correct Answer: B — 2, 3, 1

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Q. What is the result of a post-order traversal on a binary tree with nodes 1, 2, and 3, where 1 is the root, 2 is the left child, and 3 is the right child?

A. 1, 2, 3
B. 2, 3, 1
C. 3, 2, 1
D. 1, 3, 2

Solution

In post-order traversal, we visit the left child, then the right child, and finally the parent. Thus, the output is 2, 3, 1.

Correct Answer: B — 2, 3, 1

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Q. What is the result of a post-order traversal on a binary tree?

A. Root, Left, Right
B. Left, Right, Root
C. Right, Left, Root
D. Left, Root, Right

Solution

In post-order traversal, the nodes are visited in the order of Left, Right, and then Root.

Correct Answer: B — Left, Right, Root

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Q. What is the result of a post-order traversal on the following binary tree: A, B, C, D?

A. A B C D
B. D C B A
C. B D C A
D. C B D A

Solution

In post-order traversal, you visit the left subtree, then the right subtree, and finally the root. Thus, for the given tree, the result is D C B A.

Correct Answer: B — D C B A

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Q. What is the result of a postorder traversal on a binary tree?

A. Root, Left, Right
B. Left, Right, Root
C. Right, Left, Root
D. Left, Root, Right

Solution

Postorder traversal visits nodes in the order: Left, Right, Root.

Correct Answer: B — Left, Right, Root

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Q. What is the result of a postorder traversal on the binary tree with root 1, left child 2, and right child 3?

A. 1, 2, 3
B. 2, 3, 1
C. 3, 2, 1
D. 1, 3, 2

Solution

Postorder traversal visits the left child, then the right child, and finally the root, resulting in the order 2, 3, 1.

Correct Answer: B — 2, 3, 1

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Q. What is the result of a pre-order traversal of the binary tree with root 1, left child 2, and right child 3?

A. 1, 2, 3
B. 2, 1, 3
C. 3, 1, 2
D. 1, 3, 2

Solution

In pre-order traversal, the root is visited first, followed by the left subtree and then the right subtree, resulting in 1, 2, 3.

Correct Answer: A — 1, 2, 3

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Q. What is the result of an in-order traversal of a binary search tree?

A. Nodes in random order
B. Nodes in descending order
C. Nodes in ascending order
D. Nodes in level order

Solution

An in-order traversal of a binary search tree results in the nodes being visited in ascending order.

Correct Answer: C — Nodes in ascending order

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Q. What is the result of an in-order traversal of the binary tree with root 1, left child 2, and right child 3?

A. 1, 2, 3
B. 2, 1, 3
C. 3, 1, 2
D. 1, 3, 2

Solution

In-order traversal visits the left child first, then the root, and finally the right child, resulting in 2, 1, 3.

Correct Answer: B — 2, 1, 3

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Q. What is the result of an inorder traversal of a binary search tree?

A. Sorted order of elements
B. Reverse sorted order of elements
C. Random order of elements
D. Level order of elements

Solution

An inorder traversal of a binary search tree results in the elements being visited in sorted order.

Correct Answer: A — Sorted order of elements

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Q. What is the result of an inorder traversal of the binary tree with root 1, left child 2, and right child 3?

A. 1, 2, 3
B. 2, 1, 3
C. 3, 1, 2
D. 1, 3, 2

Solution

Inorder traversal visits the left child first, then the root, and finally the right child, resulting in 2, 1, 3.

Correct Answer: B — 2, 1, 3

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Q. What is the result of applying dynamic programming to the Coin Change problem?

A. Finding the minimum number of coins
B. Finding all possible combinations of coins
C. Finding the maximum value of coins
D. Finding the average value of coins

Solution

Dynamic programming can be used to find the minimum number of coins needed to make a certain amount in the Coin Change problem.

Correct Answer: A — Finding the minimum number of coins

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Q. What is the result of binary search if the array is empty?

A. Returns 0
B. Returns -1
C. Returns null
D. Throws an error

Solution

If the array is empty, binary search will return -1, indicating that the target is not found.

Correct Answer: B — Returns -1

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Q. What is the result of binary search if the target is less than the middle element?

A. Search the left half
B. Search the right half
C. Return the middle element
D. End the search

Solution

If the target is less than the middle element, binary search continues the search in the left half of the array.

Correct Answer: A — Search the left half

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Q. What is the result of performing a binary search on the array [2, 4, 6, 8, 10] for the value 5?

A. 5
B. 4
C. 6
D. Not found

Solution

The value 5 is not present in the array, so the result of the binary search would be 'Not found'.

Correct Answer: D — Not found

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Q. What is the result of performing binary search on a sorted array for an element not present in the array?

A. The index of the closest element
B. The index of the first element
C. The index of the last element
D. An indication that the element is not found

Solution

Binary search will indicate that the element is not found, typically returning a sentinel value or -1.

Correct Answer: D — An indication that the element is not found

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Q. What is the result of performing binary search on an array with duplicate values?

A. First occurrence of the value
B. Last occurrence of the value
C. Any occurrence of the value
D. None of the above

Solution

Binary search can return any occurrence of the target value when duplicates are present, depending on the implementation.

Correct Answer: C — Any occurrence of the value

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Q. What is the result of popping an element from an empty stack?

A. The top element is returned
B. An error is thrown
C. The stack remains unchanged
D. The stack is cleared

Solution

Popping an element from an empty stack typically results in an error being thrown, as there are no elements to remove.

Correct Answer: B — An error is thrown

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Q. What is the result of the following binary search on the array [1, 2, 3, 4, 5] for target 3?

A. 0
B. 1
C. 2
D. 3

Solution

The target 3 is located at index 2 in the array [1, 2, 3, 4, 5].

Correct Answer: C — 2

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Q. What is the role of the 'visited' set in Dijkstra's algorithm?

A. To keep track of the nodes that have been processed
B. To store the shortest path distances
C. To maintain the priority queue
D. To count the number of edges

Solution

The 'visited' set in Dijkstra's algorithm keeps track of the nodes that have already been processed to avoid reprocessing them.

Correct Answer: A — To keep track of the nodes that have been processed

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Q. What is the space complexity of a breadth-first traversal of a binary tree?

A. O(n)
B. O(log n)
C. O(1)
D. O(n log n)

Solution

The space complexity of a breadth-first traversal is O(n) because it needs to store all nodes at the current level in the queue.

Correct Answer: A — O(n)

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Q. What is the space complexity of a linked list with n nodes?

A. O(1)
B. O(n)
C. O(n log n)
D. O(n^2)

Solution

The space complexity of a linked list with n nodes is O(n) because each node requires space.

Correct Answer: B — O(n)

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Q. What is the space complexity of a linked list?

A. O(1)
B. O(n)
C. O(log n)
D. O(n^2)

Solution

A linked list requires space for each node, which is proportional to the number of elements, leading to a space complexity of O(n).

Correct Answer: B — O(n)

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Data Structures & Algorithms

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