Walmart Labs coding interview
questions, leaked.
122 problems reported across recent Walmart Labs interviews. Top patterns: array, string, hash table. The list below is what most candidates actually saw, plus the honest play if you can't grind all of it.
Walmart Labs hits you with 122 problems across 67 percent medium difficulty. Arrays dominate the pool (62 problems), followed by strings (32) and hash tables (27). You're looking at a diet of two-pointers, dynamic programming, and design problems like LRU Cache and Max Stack. The good news: most questions test patterns you've seen before. The bad news: you need speed and zero errors under pressure. If you freeze mid-OA on a hash-table variant, StealthCoder runs invisibly and surfaces a working solution in seconds.
Top problems at Walmart Labs
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Longest Substring Without Repeating Characters | MEDIUM | 100.0 | 37% | Hash Table · String · Sliding Window |
| 02 | LRU Cache | MEDIUM | 96.3 | 45% | Hash Table · Linked List · Design |
| 03 | Valid Parentheses | EASY | 86.5 | 42% | String · Stack |
| 04 | Max Stack | HARD | 84.9 | 46% | Linked List · Stack · Design |
| 05 | Trapping Rain Water | HARD | 81.5 | 65% | Array · Two Pointers · Dynamic Programming |
| 06 | Merge Intervals | MEDIUM | 81.5 | 49% | Array · Sorting |
| 07 | Best Time to Buy and Sell Stock | EASY | 79.5 | 55% | Array · Dynamic Programming |
| 08 | Word Break | MEDIUM | 77.4 | 48% | Array · Hash Table · String |
| 09 | Two Sum | EASY | 77.4 | 56% | Array · Hash Table |
| 10 | Longest Palindromic Substring | MEDIUM | 77.4 | 36% | Two Pointers · String · Dynamic Programming |
| 11 | Divide Intervals Into Minimum Number of Groups | MEDIUM | 77.4 | 64% | Array · Two Pointers · Greedy |
| 12 | Generate Parentheses | MEDIUM | 75.1 | 77% | String · Dynamic Programming · Backtracking |
| 13 | Minimum Number of Operations to Make Arrays Similar | HARD | 75.1 | 60% | Array · Greedy · Sorting |
| 14 | Count Good Triplets in an Array | HARD | 75.1 | 66% | Array · Binary Search · Divide and Conquer |
| 15 | Minimum Operations to Make Array Equal II | MEDIUM | 75.1 | 32% | Array · Math · Greedy |
| 16 | Maximum Number of Tasks You Can Assign | HARD | 75.1 | 51% | Array · Two Pointers · Binary Search |
| 17 | Middle of the Linked List | EASY | 75.1 | 81% | Linked List · Two Pointers |
| 18 | Number of Ways to Separate Numbers | HARD | 75.1 | 21% | String · Dynamic Programming · Suffix Array |
| 19 | The Winner University | EASY | 75.1 | 75% | Database |
| 20 | Number of Islands | MEDIUM | 72.6 | 62% | Array · Depth-First Search · Breadth-First Search |
| 21 | Search in Rotated Sorted Array | MEDIUM | 72.6 | 43% | Array · Binary Search |
| 22 | Group Anagrams | MEDIUM | 72.6 | 71% | Array · Hash Table · String |
| 23 | Kth Largest Element in an Array | MEDIUM | 72.6 | 68% | Array · Divide and Conquer · Sorting |
| 24 | Spiral Matrix | MEDIUM | 72.6 | 54% | Array · Matrix · Simulation |
| 25 | Longest Consecutive Sequence | MEDIUM | 69.8 | 47% | Array · Hash Table · Union Find |
| 26 | Sort Colors | MEDIUM | 69.8 | 68% | Array · Two Pointers · Sorting |
| 27 | Coin Change | MEDIUM | 66.5 | 46% | Array · Dynamic Programming · Breadth-First Search |
| 28 | Binary Tree Zigzag Level Order Traversal | MEDIUM | 66.5 | 62% | Tree · Breadth-First Search · Binary Tree |
| 29 | Combination Sum | MEDIUM | 66.5 | 75% | Array · Backtracking |
| 30 | Valid Sudoku | MEDIUM | 66.5 | 62% | Array · Hash Table · Matrix |
| 31 | Move Zeroes | EASY | 66.5 | 63% | Array · Two Pointers |
| 32 | Pow(x, n) | MEDIUM | 62.8 | 37% | Math · Recursion |
| 33 | 3Sum | MEDIUM | 62.8 | 37% | Array · Two Pointers · Sorting |
| 34 | Median of Two Sorted Arrays | HARD | 62.8 | 44% | Array · Binary Search · Divide and Conquer |
| 35 | All Nodes Distance K in Binary Tree | MEDIUM | 62.8 | 66% | Hash Table · Tree · Depth-First Search |
| 36 | Degree of an Array | EASY | 62.8 | 57% | Array · Hash Table |
| 37 | Rotate Array | MEDIUM | 62.8 | 43% | Array · Math · Two Pointers |
| 38 | Top K Frequent Elements | MEDIUM | 62.8 | 65% | Array · Hash Table · Divide and Conquer |
| 39 | Word Search | MEDIUM | 58.5 | 45% | Array · String · Backtracking |
| 40 | Flatten Nested List Iterator | MEDIUM | 58.5 | 65% | Stack · Tree · Depth-First Search |
| 41 | Daily Temperatures | MEDIUM | 58.5 | 67% | Array · Stack · Monotonic Stack |
| 42 | LFU Cache | HARD | 58.5 | 47% | Hash Table · Linked List · Design |
| 43 | House Robber | MEDIUM | 58.5 | 52% | Array · Dynamic Programming |
| 44 | Copy List with Random Pointer | MEDIUM | 58.5 | 61% | Hash Table · Linked List |
| 45 | First Missing Positive | HARD | 58.5 | 41% | Array · Hash Table |
| 46 | Reverse Nodes in k-Group | HARD | 58.5 | 63% | Linked List · Recursion |
| 47 | Add Binary | EASY | 58.5 | 56% | Math · String · Bit Manipulation |
| 48 | Merge k Sorted Lists | HARD | 58.5 | 57% | Linked List · Divide and Conquer · Heap (Priority Queue) |
| 49 | Search a 2D Matrix | MEDIUM | 58.5 | 52% | Array · Binary Search · Matrix |
| 50 | Longest Common Prefix | EASY | 58.5 | 45% | String · Trie |
Frequencies derived from public community-tagged interview reports. Click a row to view on LeetCode.
You have a week, maybe less. You can't out-grind the list above. StealthCoder runs invisibly during the actual Walmart Labs OA. The proctor cannot see it. Screen share cannot detect it. Built by an Amazon engineer who used it to pass JPMorgan's OA and system design loop.
Get StealthCoder- array62 · 51%
- string32 · 26%
- hash table27 · 22%
- dynamic programming24 · 20%
- two pointers20 · 16%
- sorting17 · 14%
- depth first search16 · 13%
- greedy14 · 11%
- breadth first search13 · 11%
- linked list12 · 10%
Array problems are the backbone of this interview. Longest Substring Without Repeating Characters, Trapping Rain Water, and Merge Intervals show Walmart cares about sliding windows, two-pointers, and sorting workflows. Strings come second (32 problems), often paired with dynamic programming or hash tables. Design questions (LRU Cache, Max Stack) test whether you understand data-structure internals, not just algorithm mechanics. Dynamic programming appears 24 times, so expect at least one hard DP problem. The median difficulty is MEDIUM (82 problems), which means breadth beats depth. Drill arrays and strings first, then lock in two-pointers and hash-table patterns. When you hit the live assessment, StealthCoder is your hedge for the one pattern you didn't have time to cover.
Companies with similar patterns
If you prepped for Walmart Labs, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass Walmart Labs.
Memorizing every problem above in a week is a fantasy. StealthCoder is the hedge: an AI overlay that's invisible during screen share. It reads the problem on screen and surfaces a working solution in under 2 seconds. Built by an Amazon engineer who used it to pass JPMorgan's OA and system design loop. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Walmart Labs interview FAQ
How many array problems should I solve before the interview?+
Arrays show up in 62 of 122 problems (51 percent of the pool). Prioritize two-pointer techniques (Trapping Rain Water, Merge Intervals) and sliding-window patterns (Longest Substring Without Repeating Characters). Aim for 15 to 20 array problems, focusing on medium difficulty. You can't cover all 62, so drill the patterns instead.
Is dynamic programming required for Walmart Labs?+
DP appears in 24 problems, including Word Break, Best Time to Buy and Sell Stock, and Longest Palindromic Substring. Most are medium difficulty. You don't need advanced DP (no tree DP or bitmask DP), but memoization and bottom-up thinking are baseline. Study 4 to 6 classic DP problems before the OA.
What should I study first, strings or hash tables?+
Strings (32 problems) edge out hash tables (27), and they're often tested together. Start with Longest Substring Without Repeating Characters and Valid Parentheses to warm up. Hash tables matter more for design problems (LRU Cache). Hit strings first for volume, hash tables second for depth.
Do I need to know design patterns like LRU Cache?+
Yes. LRU Cache and Max Stack are both in the top problems, signaling Walmart tests system design at the medium-hard level. These aren't algorithm problems. You need to understand data-structure tradeoffs and doubly-linked list plus hash-table combos. Budget 3 to 4 hours on design-specific prep.
How do I prepare for the 17 hard problems?+
Hards are 14 percent of the pool (17 of 122). They lean on Trapping Rain Water, Max Stack, Count Good Triplets, and advanced sorting. Don't memorize hard problems. Instead, master the medium patterns so thoroughly that you can adapt them under pressure. If you hit an unfamiliar hard on test day, StealthCoder backs you up.