Variable Naming in Algorithms for Coding Interviews

Variable naming in algorithms is a silent skill in coding interviews. Instead of naming a variable "i", if you give it a meaningful name like "lastKnownDuplicate", it will help you keep track of the meaning of that variable, like labeling storage boxes.

Here are some charts and tips to help you with naming variables as you prepare (with some help from ai and Grokking the Coding Interview).

🗂 Grokking Patterns + Variable Names (Quick Glance)

Pattern	Go-To Variable Names
Sliding Window	windowStart, windowEnd, windowSum, charFrequency
Two Pointers	left, right, targetSum, lastNonDuplicate
Fast & Slow Pointers	slowPointer, fastPointer, cycleStart
Merge Intervals	currentInterval, mergedIntervals, intervalStart, intervalEnd
Cyclic Sort	currentIndex, correctIndex
In-place Linked List Reversal	currentNode, previousNode, nextNode
Tree BFS	queue, nodeQueue, currentNode, levelSize, levels
Tree DFS	currentPath, allPaths, remainingSum
Two Heaps	maxHeap, minHeap, median
Subsets / Backtracking	currentSubset, subsets, startIndex
Modified Binary Search	start, end, mid, target
Top K Elements	minHeap, maxHeap, topKElements, distance

🗂 Grokking Patterns + Variable Names (In-Depth)

Sliding Window

Role	Good Name	Notes
Start index of window	windowStart	First element in current range
End index of window	windowEnd	Last element in current range
Frequency counter	charFrequency, numFrequency	Use type-specific name
Current sum/length	windowSum, windowLength	Describes what’s being aggregated

Two Pointers

Role	Good Name	Notes
Left pointer	left or start	Works for arrays and strings
Right pointer	right or end
Target sum	targetSum	Use when looking for sum
Last valid position	lastNonDuplicate, lastSorted	Clarifies purpose

Fast & Slow Pointers

Role	Good Name	Notes
Slow pointer	slowPointer	Advances 1 step at a time
Fast pointer	fastPointer	Advances 2 steps at a time
Cycle start	cycleStart	For cycle detection problems

Merge Intervals

Role	Good Name	Notes
Current interval	currentInterval	Often a tuple/array [start, end]
Merged result list	mergedIntervals	Plural for clarity
Interval start/end	intervalStart, intervalEnd	Explicit meaning

Cyclic Sort

Role	Good Name	Notes
Current index	currentIndex	Avoid i
Correct index for value	correctIndex	Makes swap logic obvious

In-place Linked List Reversal

Role	Good Name	Notes
Current node	currentNode	Where we are now
Previous node	previousNode	Node before current
Next node	nextNode	Node after current

Tree BFS

Role	Good Name	Notes
Processing queue	queue or nodeQueue	BFS uses queues
Current node	currentNode
Current level size	levelSize	Used to group levels
Result list	result, levels	Use plural for collection

Tree DFS

Role	Good Name	Notes
Current path	currentPath	For backtracking
All paths	allPaths	For collecting results
Remaining sum	remainingSum	For path sum problems

Two Heaps

Role	Good Name	Notes
Small half	maxHeap	Stores smaller numbers
Large half	minHeap	Stores larger numbers
Median	median	Optional if caching

Subsets / Backtracking

Role	Good Name	Notes
Current subset	currentSubset	Or subset if short-lived
Result list	subsets or result	Plural for clarity
Start index	startIndex	For recursive calls

Modified Binary Search

Role	Good Name	Notes
Search start	start	Lower bound index
Search end	end	Upper bound index
Midpoint	mid	Middle index
Target value	target	What we’re searching for

Top K Elements

Role	Good Name	Notes
Heap	minHeap or maxHeap	Match name to type used
Result list	topKElements	Describes final goal
Distance function	distance	For closest point problems

🗂 Grokking Patterns + Variable Names (Quick Tips)

1. Role + Context
   Instead of i, say what it is and why it’s there.

   ❌ i → ✔ windowStart
   ❌ j → ✔ windowEnd
   ❌ count → ✔ charFrequency

2. Relationship to Other Variables
   If there’s a pair, name them so they “talk to each other.”

   fastPointer / slowPointer
   minHeap / maxHeap
   left / right

3. Avoid Mental Gymnastics
   If a name makes you stop and translate it in your head, it’s too short or too vague.

   ❌ ptr → ✔ currentNode
   ❌ n1, n2 → ✔ intervalStart, intervalEnd