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GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

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Data Structures and Algorithms → Sorting Algorithms 1

In insertion sort, what does pos=pos-1 do?
Moves position left to find insertion spot
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Data Structures and Algorithms → Stack 10

Stack follows which principle?
LIFO
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Stack is used in compilers for?
Syntax parsing
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Stack is used for undo/redo in?
Text editors and IDEs
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In stack using linked list, new node is added at?
Tail (last node)
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Which notation does stack evaluate naturally?
Postfix (Reverse Polish)
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Stack Underflow in linked list stack returns:
-1000
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Maximum elements in stack of size n after n pushes?
n
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In push(s,n) when stack empty: S.head=n and S.top=?
n
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Which application uses stack for backtracking?
Browser back/forward navigation
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Stack type — linear or non-linear?
Linear
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Data Structures and Algorithms → Introduction to DSA 19

Operation to add element to stack?
Push
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Operation to remove element from stack?
Pop
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Python list method to push onto stack?
append()
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Python list method to pop from stack?
pop()
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Error when popping from empty stack?
Stack Underflow
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Error when pushing to full array-based stack?
Stack Overflow
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What does peek() do on a stack?
Returns top without removing
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Time complexity of push and pop on a stack?
O(1)
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Real-world example of a stack?
Pile of plates
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Evaluate postfix '2 3 + 4 *':
20
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Minimum stacks needed to implement a queue?
2
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Infix A+B*C in postfix is?
ABC*+
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Evaluate postfix '5 1 2 + 4 * + 3 -':
14
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When top==null in stack?
Stack is empty
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What does IS_EMPTY check in a stack?
S.top==null
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Activation record of a function is stored in?
Stack memory (call stack)
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After push(10),push(20),push(30),pop() — top is?
20
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Operation to add element to queue?
Enqueue
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Operation to remove element from queue?
Dequeue
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Data Structures and Algorithms → Recursion 1

In recursion, each recursive call:
Adds frame to call stack
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Data Structures and Algorithms → Graphs 1

DFS uses which data structure?
Stack
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Data Structures and Algorithms → Linked List 1

In linked list stack, when list empty after pop, top and head are:
Both set to NULL
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Data Structures and Algorithms → Queue 7

Queue follows which principle?
FIFO
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New elements in queue are inserted at?
Rear (tail)
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Elements removed from queue from?
Front (head)
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Queue Overflow means?
Add to full queue
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Queue Underflow means?
Dequeue from empty queue
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In circular queue, when tail reaches last position, it wraps to?
1 (beginning)
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Array-based queue is empty when?
Q.tail==Q.head
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