PROBLEMS/TWO POINTERS
Two Pointers LeetCode Problems
138 hand-tagged Two Pointers problems across 3 interview patterns (Opposite-Direction (Converging), Same-Direction (Fast/Slow on Arrays), K-Sum Pattern (3Sum, 4Sum)), ranked by importance (how often each pattern shows up in real coding interviews). Work top-down within each pattern.
| # | PROBLEM | DIFF | ELO | IMP | PATTERNS |
|---|---|---|---|---|---|
| 1 | Trapping Rain Water | Medium | 1699 | 93 | Monotonic Stack · Prefix Sums |
| 2 | Two Sum II - Input Array Is Sorted | Easy | 1124 | 90 | Complement Search (Two Sum Pattern) |
| 3 | Container With Most Water | Easy | 1374 | 90 | Exchange Argument / Local Adjustment |
| 4 | Valid Palindrome | Easy | 1045 | 85 | |
| 5 | Longest Palindromic Substring | Medium | 1458 | 84 | Word Break / String DP |
| # | PROBLEM | DIFF | ELO | IMP | PATTERNS |
|---|---|---|---|---|---|
| 1 | Merge Sorted Array | Easy | 1101 | 82 | |
| 2 | Remove Duplicates from Sorted Array | Easy | 1102 | 82 | Sorting + Comparison |
| 3 | Find the Duplicate Number | Medium | 1551 | 82 | Binary Search on Answer Space · Fast/Slow Pointers (Cycle, Middle) |
| 4 | Move Zeroes | Easy | 1032 | 78 | Opposite-Direction (Converging) |
| 5 | Remove Element | Easy | 1067 | 78 | Frequency Counting / Hash Map Lookup |
| # | PROBLEM | DIFF | ELO | IMP | PATTERNS |
|---|---|---|---|---|---|
| 1 | 3Sum | Medium | 1534 | 91 | Sorting + Comparison · Complement Search (Two Sum Pattern) |
| 2 | 4Sum | Medium | 1581 | 72 | Sorting + Comparison |
| 3 | 3Sum SmallerPREMIUM | Easy | 1378 | 62 | Sorting + Comparison · Standard Binary Search |
| 4 | 3Sum Closest | Medium | 1427 | 58 | Sorting + Comparison |
| 5 | 3Sum With Multiplicity | Medium | 1711 | 53 | Frequency Counting / Hash Map Lookup · Combinatorics |
EVERY PATTERN
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