ARRAYS & STRINGS – PROBLEM LIST

Here is a curated, leveled problem list for MODULE 1: ARRAYS & STRINGS Designed for progressive learning → Beginner → Intermediate → Advanced Includes LeetCode (LC), GeeksforGeeks (GFG), Codeforces (CF), and InterviewBit (IB) links.

ARRAYS & STRINGS – PROBLEM LIST

ARRAYS & STRINGS – PROBLEM LIST

Here is a curated, leveled problem list for MODULE 1: ARRAYS & STRINGS
Designed for progressive learning → Beginner → Intermediate → Advanced
Includes LeetCode (LC), GeeksforGeeks (GFG), Codeforces (CF), and InterviewBit (IB) links.

MODULE 1: ARRAYS & STRINGS – PROBLEM LIST

# Problem Name Platform Difficulty Key Technique Link
1 Two Sum LC Easy Hash Map LC 1
2 Best Time to Buy and Sell Stock LC Easy One-pass (min so far) LC 121
3 Contains Duplicate LC Easy Set / Sorting LC 217
4 Move Zeroes LC Easy Two Pointers (in-place) LC 283
5 Rotate Array LC Easy Reverse trick / Juggling LC 189
6 Maximum Subarray (Kadane) LC Medium DP (optimized) LC 53
7 Merge Sorted Array LC Easy Two pointers from end LC 88
8 Remove Duplicates from Sorted Array LC Easy Two pointers LC 26
9 Trapping Rain Water LC Hard Two pointers / Precompute LC 42
10 3Sum LC Medium Sort + Two Pointers LC 15
11 Container With Most Water LC Medium Two pointers (greedy) LC 11
12 Longest Substring Without Repeating Characters LC Medium Sliding Window + Set/Map LC 3
13 Longest Palindromic Substring LC Medium Expand around center / DP LC 5
14 Merge Intervals LC Medium Sort + Merge LC 56
15 Sort Colors (0,1,2) LC Medium Dutch National Flag (3 pointers) LC 75
16 Subarray Sum Equals K LC Medium Prefix Sum + Hash Map LC 560
17 Minimum Size Subarray Sum LC Medium Sliding Window LC 209
18 Product of Array Except Self LC Medium Prefix & Suffix Product LC 238
19 Find the Duplicate Number LC Medium Floyd’s Cycle / Binary Search LC 287
20 Spiral Matrix LC Medium Layer-by-layer simulation LC 54

BONUS: STRING-SPECIFIC PROBLEMS

# Problem Platform Technique Link
B1 Valid Anagram LC Hash Map / Sorting LC 242
B2 Longest Common Prefix LC Vertical scan / Trie LC 14
B3 Implement strStr() (KMP) LC KMP / Sliding LC 28
B4 Ransom Note LC Hash Map LC 383
B5 Group Anagrams LC Hash Map with sorted key LC 49

PRACTICE PLAN (4 Weeks)

Week Focus Problems
1 Basics + Two Pointers 1–8
2 Sliding Window + Prefix 9–13, 16–17
3 Advanced Two Pointers 10, 11, 14, 15, 18
4 Hard + Strings 19, 20, B1–B5

TIPS

  • Solve in order → build intuition.
  • Re-solve without hints after 3 days.
  • Time yourself: Easy < 10 min, Medium < 20 min.
  • Write clean code → use meaningful variable names.
  • Dry run on small test cases.

Want this as a printable PDF or Notion table?
Or need solutions + explanations for any problem? Just ask!

Last updated: Nov 10, 2025

ARRAYS & STRINGS – PROBLEM LIST

Here is a curated, leveled problem list for MODULE 1: ARRAYS & STRINGS Designed for progressive learning → Beginner → Intermediate → Advanced Includes LeetCode (LC), GeeksforGeeks (GFG), Codeforces (CF), and InterviewBit (IB) links.

ARRAYS & STRINGS – PROBLEM LIST

ARRAYS & STRINGS – PROBLEM LIST

Here is a curated, leveled problem list for MODULE 1: ARRAYS & STRINGS
Designed for progressive learning → Beginner → Intermediate → Advanced
Includes LeetCode (LC), GeeksforGeeks (GFG), Codeforces (CF), and InterviewBit (IB) links.

MODULE 1: ARRAYS & STRINGS – PROBLEM LIST

# Problem Name Platform Difficulty Key Technique Link
1 Two Sum LC Easy Hash Map LC 1
2 Best Time to Buy and Sell Stock LC Easy One-pass (min so far) LC 121
3 Contains Duplicate LC Easy Set / Sorting LC 217
4 Move Zeroes LC Easy Two Pointers (in-place) LC 283
5 Rotate Array LC Easy Reverse trick / Juggling LC 189
6 Maximum Subarray (Kadane) LC Medium DP (optimized) LC 53
7 Merge Sorted Array LC Easy Two pointers from end LC 88
8 Remove Duplicates from Sorted Array LC Easy Two pointers LC 26
9 Trapping Rain Water LC Hard Two pointers / Precompute LC 42
10 3Sum LC Medium Sort + Two Pointers LC 15
11 Container With Most Water LC Medium Two pointers (greedy) LC 11
12 Longest Substring Without Repeating Characters LC Medium Sliding Window + Set/Map LC 3
13 Longest Palindromic Substring LC Medium Expand around center / DP LC 5
14 Merge Intervals LC Medium Sort + Merge LC 56
15 Sort Colors (0,1,2) LC Medium Dutch National Flag (3 pointers) LC 75
16 Subarray Sum Equals K LC Medium Prefix Sum + Hash Map LC 560
17 Minimum Size Subarray Sum LC Medium Sliding Window LC 209
18 Product of Array Except Self LC Medium Prefix & Suffix Product LC 238
19 Find the Duplicate Number LC Medium Floyd’s Cycle / Binary Search LC 287
20 Spiral Matrix LC Medium Layer-by-layer simulation LC 54

BONUS: STRING-SPECIFIC PROBLEMS

# Problem Platform Technique Link
B1 Valid Anagram LC Hash Map / Sorting LC 242
B2 Longest Common Prefix LC Vertical scan / Trie LC 14
B3 Implement strStr() (KMP) LC KMP / Sliding LC 28
B4 Ransom Note LC Hash Map LC 383
B5 Group Anagrams LC Hash Map with sorted key LC 49

PRACTICE PLAN (4 Weeks)

Week Focus Problems
1 Basics + Two Pointers 1–8
2 Sliding Window + Prefix 9–13, 16–17
3 Advanced Two Pointers 10, 11, 14, 15, 18
4 Hard + Strings 19, 20, B1–B5

TIPS

  • Solve in order → build intuition.
  • Re-solve without hints after 3 days.
  • Time yourself: Easy < 10 min, Medium < 20 min.
  • Write clean code → use meaningful variable names.
  • Dry run on small test cases.

Want this as a printable PDF or Notion table?
Or need solutions + explanations for any problem? Just ask!

Last updated: Nov 10, 2025