This document lists all array problems from the DSA Notes & Problems repository, organized by file and difficulty level.

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1. Array_problems.js
2. Array_problems1.js
3. Array_problems2.js

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#	Problem	Topics	File
1	Two Sum	Hash Map, Two Pointers	Array_problems.js
2	Palindrome	Two Pointers, String Reversal	Array_problems.js
3	Reverse String	String Manipulation, Two Pointers	Array_problems.js
4	Merge Sorted Array	Two Pointers, Merging	Array_problems.js
5	Valid Parentheses	Stack Data Structure	Array_problems.js

Key Concepts:

• Hash Map for O(n) lookups
• Two Pointer technique
• Stack-based validation

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#	Problem	Topics	File
1	Remove Duplicates from Sorted Array	Two Pointers, In-place modification	Array_problems1.js
2	Left Rotate Array by One	Array Shifting	Array_problems1.js
3	Left Rotate Array by K Places	Reversal Algorithm	Array_problems1.js
4	Move Zeros to End	Two Pointers	Array_problems1.js
5	Rotate Array (Right Rotation)	Reversal Algorithm	Array_problems1.js

Key Concepts:

• In-place array manipulation
• Rotation algorithms (forward & reverse)
• Two pointer technique for reordering

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#	Problem	Topics	File
1	Find the Largest Element in Array	Linear Scan	Array_problems2.js
2	Find the Minimum Element in Array	Linear Scan	Array_problems2.js
3	Find the Second Largest Element	Single Pass	Array_problems2.js
4	Find the Nth Largest Element	Sorting	Array_problems2.js
5	Find the Nth Minimum Element	Sorting	Array_problems2.js
6	Check if Array is Sorted	Linear Scan	Array_problems2.js

Key Concepts:

• Linear scanning techniques
• Sorting for selection problems
• Min/Max tracking patterns

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Problem	Best	Average	Worst
Two Sum (Hash)	O(n)	O(n)	O(n)
Palindrome	O(1)	O(n)	O(n)
Merge Sorted	O(n+m)	O(n+m)	O(n+m)
Remove Duplicates	O(n)	O(n)	O(n)
Rotate Array	O(n)	O(n)	O(n)
Find Largest	O(n)	O(n)	O(n)
Find Nth Largest	O(n)	O(n log n)	O(n log n)

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• Find the Largest Element
• Find the Minimum Element
• Check if Array is Sorted

• Two Sum
• Palindrome
• Merge Sorted Array
• Remove Duplicates
• Move Zeros to End

• Rotate Array (K Places)
• Valid Parentheses
• Find Second Largest
• Find Nth Largest/Minimum

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• Data Structures: Arrays, Hash Maps, Stacks
• Techniques: Two Pointers, Hash Maps, Sorting, Reversal, Linear Scan
• Concepts: In-place modification, O(1) space complexity, O(n) time complexity
• Patterns: Min/Max tracking, Merging, Rotation, Validation

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Total Problems: 16
Total Approaches Covered: 25+
Recommended Practice Order: Array_problems2.js → Array_problems.js → Array_problems1.js