American Express coding interview
questions, leaked.
23 problems reported across recent American Express interviews. Top patterns: array, hash table, string. The list below is what most reported candidates actually saw, plus the honest play if you can't grind all of it.
American Express coding interviews lean hard on arrays. Of 23 problems in their reported set, 15 are array-focused, often paired with hash tables or bit manipulation. The difficulty split is 7 easy, 12 medium, 4 hard. You'll see Two Sum, 3Sum, and array-slicing problems mixed with harder variants like Maximum Equal Frequency and Divide an Array Into Subarrays With Minimum Cost II. If you blank mid-OA on a hash-table or greedy array trick, StealthCoder solves it invisibly while you're screen-shared. The real edge is drilling arrays and hash tables first, then knowing when to reach for two-pointers or bit ops.
Top problems at American Express
| # | Problem | Diff | Frequency | Pass % | Patterns |
|---|---|---|---|---|---|
| 01 | Minimum Deletions to Make Character Frequencies Unique | MEDIUM | 100.0 | 61% | Hash Table · String · Greedy |
| 02 | Maximum Equal Frequency | HARD | 97.9 | 37% | Array · Hash Table |
| 03 | Minimum Number of Operations to Make Array XOR Equal to K | MEDIUM | 95.5 | 85% | Array · Bit Manipulation |
| 04 | Ugly Number III | MEDIUM | 95.5 | 30% | Math · Binary Search · Combinatorics |
| 05 | Divide an Array Into Subarrays With Minimum Cost I | EASY | 95.5 | 66% | Array · Sorting · Enumeration |
| 06 | Percentage of Letter in String | EASY | 95.5 | 74% | String |
| 07 | Divide an Array Into Subarrays With Minimum Cost II | HARD | 95.5 | 30% | Array · Hash Table · Sliding Window |
| 08 | Maximum XOR After Operations | MEDIUM | 95.5 | 79% | Array · Math · Bit Manipulation |
| 09 | Equal Sum Arrays With Minimum Number of Operations | MEDIUM | 95.5 | 54% | Array · Hash Table · Greedy |
| 10 | Find a Value of a Mysterious Function Closest to Target | HARD | 95.5 | 46% | Array · Binary Search · Bit Manipulation |
| 11 | Maximize the Topmost Element After K Moves | MEDIUM | 95.5 | 23% | Array · Greedy |
| 12 | Two Sum | EASY | 82.9 | 56% | Array · Hash Table |
| 13 | Valid Anagram | EASY | 72.9 | 67% | Hash Table · String · Sorting |
| 14 | 3Sum | MEDIUM | 72.9 | 37% | Array · Two Pointers · Sorting |
| 15 | Rotate Array | MEDIUM | 65.8 | 43% | Array · Math · Two Pointers |
| 16 | Best Time to Buy and Sell Stock | EASY | 65.8 | 55% | Array · Dynamic Programming |
| 17 | Valid Palindrome | EASY | 65.8 | 51% | Two Pointers · String |
| 18 | Add Digits | EASY | 65.8 | 68% | Math · Simulation · Number Theory |
| 19 | Minimum Fuel Cost to Report to the Capital | MEDIUM | 65.8 | 64% | Tree · Depth-First Search · Breadth-First Search |
| 20 | Trapping Rain Water | HARD | 55.9 | 65% | Array · Two Pointers · Dynamic Programming |
| 21 | Reconstruct a 2-Row Binary Matrix | MEDIUM | 55.9 | 48% | Array · Greedy · Matrix |
| 22 | Longest Substring Without Repeating Characters | MEDIUM | 55.9 | 37% | Hash Table · String · Sliding Window |
| 23 | Permutations | MEDIUM | 55.9 | 81% | Array · Backtracking |
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 American Express OA. The proctor cannot see it. Screen share cannot detect it. Built by a senior engineer who knows the OA is theater. This is the script.
Get StealthCoder- array15 · 65%
- hash table7 · 30%
- string5 · 22%
- math4 · 17%
- two pointers4 · 17%
- greedy4 · 17%
- sorting4 · 17%
- bit manipulation3 · 13%
- dynamic programming2 · 9%
- number theory2 · 9%
Arrays dominate the American Express pipeline, appearing in roughly 65 percent of problems. Hash tables and strings are secondary supports. The median difficulty is medium, so expect most problems to require combining two or three patterns in a single solution. Bit manipulation shows up often enough (3 problems) that skipping it will hurt. Two-pointers and greedy each appear in 4 problems, often on array rearrangement or optimization tasks. The hard problems (Divide an Array Into Subarrays With Minimum Cost II, Maximum Equal Frequency, Find a Value of a Mysterious Function Closest to Target) mix arrays with sliding windows, binary search, or bit logic. If you've never solved Minimum Deletions to Make Character Frequencies Unique or Maximum XOR After Operations, run those now. StealthCoder is your safety net if you hit a wall on the bit-manipulation variants or a novel greedy angle during the live assessment.
Companies with similar patterns
If you prepped for American Express, these companies recycle ~60% of the same topics.
You've seen the list.
Now make sure you pass American Express.
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 a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
American Express interview FAQ
Should I focus on arrays first for American Express?+
Yes. Arrays appear in 15 of 23 problems. Start with Two Sum, 3Sum, and Rotate Array to build muscle memory. Then layer in hash-table lookups and two-pointer techniques. Skip this and you're unprepared for 65 percent of their set.
How important is bit manipulation for this company?+
Important enough to not ignore. Three problems explicitly require bit ops, including hard problems like Find a Value of a Mysterious Function Closest to Target. If you're weak on XOR and bit tricks, drill Minimum Number of Operations to Make Array XOR Equal to K and Maximum XOR After Operations before your OA.
What should I practice if I only have a week?+
Prioritize: Two Sum, 3Sum, Rotate Array, Minimum Deletions to Make Character Frequencies Unique, and Divide an Array Into Subarrays With Minimum Cost I. These cover array, hash-table, greedy, and sorting fundamentals. Then tackle one hard problem daily from the remaining list.
Are the hard problems really that much harder?+
Yes. The four hard problems (Maximum Equal Frequency, Divide an Array Into Subarrays With Minimum Cost II, Find a Value of a Mysterious Function Closest to Target) combine arrays with advanced techniques like sliding windows, binary search, or segment trees. They're not just extensions of medium problems. Expect one in your OA.
Do I need to know sliding window for American Express?+
Only two problems explicitly use sliding window, but it appears in one hard problem (Divide an Array Into Subarrays With Minimum Cost II). If your array skills are solid and you understand greedy optimization, you can learn sliding window on-demand. It's not a blocker.