American Express Interview Questions — 23 DSA Problems

23 problems with full solutions in Python, Java, C++, JavaScript, Go, Rust.

Most frequently asked American Express LeetCode questions for software engineering interviews.

• Minimum Deletions to Make Character Frequencies Unique (MEDIUM) — Hash Table, String, Greedy, Sorting
• Maximum Equal Frequency (HARD) — Array, Hash Table
• Percentage of Letter in String (EASY) — String
• Minimum Number of Operations to Make Array XOR Equal to K (MEDIUM) — Array, Bit Manipulation
• Equal Sum Arrays With Minimum Number of Operations (MEDIUM) — Array, Hash Table, Greedy, Counting
• Find a Value of a Mysterious Function Closest to Target (HARD) — Array, Binary Search, Bit Manipulation, Segment Tree
• Maximum XOR After Operations (MEDIUM) — Array, Math, Bit Manipulation
• Divide an Array Into Subarrays With Minimum Cost II (HARD) — Array, Hash Table, Sliding Window, Heap (Priority Queue)
• Divide an Array Into Subarrays With Minimum Cost I (EASY) — Array, Sorting, Enumeration
• Maximize the Topmost Element After K Moves (MEDIUM) — Array, Greedy
• Ugly Number III (MEDIUM) — Math, Binary Search, Combinatorics, Number Theory
• Two Sum (EASY) — Array, Hash Table
• 3Sum (MEDIUM) — Array, Two Pointers, Sorting
• Valid Anagram (EASY) — Hash Table, String, Sorting
• Minimum Fuel Cost to Report to the Capital (MEDIUM) — Tree, Depth-First Search, Breadth-First Search, Graph
• Add Digits (EASY) — Math, Simulation, Number Theory
• Valid Palindrome (EASY) — Two Pointers, String
• Rotate Array (MEDIUM) — Array, Math, Two Pointers
• Best Time to Buy and Sell Stock (EASY) — Array, Dynamic Programming
• Reconstruct a 2-Row Binary Matrix (MEDIUM) — Array, Greedy, Matrix
• Trapping Rain Water (HARD) — Array, Two Pointers, Dynamic Programming, Stack, Monotonic Stack
• Longest Substring Without Repeating Characters (MEDIUM) — Hash Table, String, Sliding Window
• Permutations (MEDIUM) — Array, Backtracking