Ace your Goldman Sachs LeetCode interview. Prepare with the top 30 most common questions asked by GS to ensure your success.
Goldman Sachs, a global leader in financial services, is renowned for its rigorous hiring process, particularly for technology roles. A critical component of these interviews involves tackling coding challenges, often drawing from platforms like LeetCode. Aspiring software engineers, data scientists, and quantitative analysts frequently face a gauntlet of questions designed to assess their proficiency in data structures, algorithms, and problem-solving. Success in these technical rounds hinges on not just knowing the answers, but understanding the underlying concepts and demonstrating clear, efficient coding practices. This article compiles 30 of the most frequently encountered Goldman Sachs LeetCode interview questions, providing actionable advice and example answers to help you navigate your preparation effectively.
What Are Goldman Sachs LeetCode Interview Questions?
Goldman Sachs LeetCode interview questions are algorithmic challenges similar to those found on the LeetCode platform, tailored to evaluate a candidate's core computer science knowledge and coding ability. These questions span various difficulty levels, from easy to hard, and cover fundamental data structures such as arrays, linked lists, trees, graphs, and hash tables, alongside essential algorithms like dynamic programming, greedy algorithms, backtracking, sorting, and searching. The problems are designed to test logical thinking, efficiency (time and space complexity), and the ability to translate conceptual solutions into clean, executable code. Familiarity with these types of problems is crucial for anyone aiming for a technical role at Goldman Sachs.
Why Do Interviewers Ask Goldman Sachs LeetCode Interview Questions?
Interviewers at Goldman Sachs utilize LeetCode-style questions for several key reasons. Firstly, they serve as a standardized method to gauge a candidate's foundational computer science understanding and problem-solving skills under pressure. The ability to break down a complex problem, identify an optimal approach, and implement it correctly reflects a candidate's analytical prowess and coding discipline. Secondly, these questions assess proficiency in efficient algorithm design, critical for building scalable and high-performance financial systems where milliseconds can count. Lastly, it evaluates how candidates communicate their thought process, articulate trade-offs, and handle edge cases—skills vital for collaborative development within a demanding environment. It’s about demonstrating robust technical competency, not just memorizing solutions.
Preview List
1. Two Sum
2. Valid Parentheses
3. Group Anagrams
4. Longest Substring Without Repeating Characters
5. Kth Largest Element in an Array
6. Trapping Rain Water
7. Fraction to Recurring Decimal
8. First Unique Character in a String
9. Design HashMap
10. Open the Lock
11. Maximum Sum Circular Subarray
12. Search in Rotated Sorted Array
13. Combination Sum
14. Jump Game II
15. Permutations
16. Minimum Path Sum
17. Climbing Stairs
18. Merge Sorted Array
19. Decode Ways
20. Validate Binary Search Tree
21. Pascal’s Triangle
22. Best Time to Buy and Sell Stock
23. Copy List with Random Pointer
24. Linked List Cycle
25. Next Permutation
26. Subsets
27. Gas Station
28. Unique Frequencies
29. Pivot Index
30. All Possible Balanced Parentheses
1. How do you find two numbers in an array that sum up to a specific target?
Why you might get asked this:
This easy problem tests your understanding of hash tables for efficient lookups, a common technique in Goldman Sachs LeetCode interview questions. It assesses basic array traversal and data structure usage.
How to answer:
Use a hash map to store numbers encountered and their indices. For each number, check if its complement (target - current_num) exists in the map.
Example answer:
Iterate through the array. For each `num`, calculate `complement = target - num`. If `complement` is in the hash map, return `[map[complement], i]`. Otherwise, add `num` and `i` to the map.
2. How do you determine if a string of parentheses is valid?
Why you might get asked this:
This problem evaluates your ability to use a stack data structure, crucial for handling nested structures and common in Goldman Sachs LeetCode interview questions.
How to answer:
Use a stack. Push opening brackets. On a closing bracket, pop from stack and check for a match. If no match or stack empty, it's invalid. Stack must be empty at the end.
Example answer:
Initialize an empty stack. Map closing brackets to opening ones. Iterate string: push opening, pop and check for matching closing. If mismatch or empty stack on pop, return false. Final stack must be empty.
3. How do you group anagrams together from a list of strings?
Why you might get asked this:
This medium-level problem tests hash map usage with string manipulation, common in Goldman Sachs LeetCode interview questions. It requires understanding of canonical forms.
How to answer:
Create a canonical form for each string (e.g., by sorting its characters). Use this sorted string as a key in a hash map to group original strings.
Example answer:
For each string, sort its characters to form a key (e.g., "eat" -> "aet"). Store original string in a list mapped to this key in a dictionary. Return all dictionary values.
4. How do you find the length of the longest substring without repeating characters?
Why you might get asked this:
This problem assesses your understanding of the sliding window technique, a fundamental pattern in Goldman Sachs LeetCode interview questions for array/string problems.
How to answer:
Use a sliding window (two pointers) and a hash set to track characters within the current window. Expand the window, and if a repeat is found, shrink from the left.
Example answer:
Use `left`, `right` pointers and a set. While `right < len(s)`: if `s[right]` not in set, add it and `right++`, update max length. Else, remove `s[left]` and `left++`.
5. How do you find the Kth largest element in an unsorted array?
Why you might get asked this:
This problem tests sorting algorithms or heap (priority queue) usage, often seen in Goldman Sachs LeetCode interview questions for efficient element retrieval.
How to answer:
Use a min-heap of size K. Iterate through the array; push elements onto the heap. If heap size exceeds K, pop the smallest element. The top of the heap is the Kth largest.
Example answer:
Build a min-heap. For each `num` in the array, `heapq.heappush(heap, num)`. If `len(heap) > k`, `heapq.heappop(heap)`. Finally, `heap[0]` is the Kth largest.
6. How do you calculate the amount of water trapped between bars after a rainfall?
Why you might get asked this:
This hard problem tests advanced two-pointer techniques or stack usage, highlighting efficient solutions often sought in Goldman Sachs LeetCode interview questions.
How to answer:
Use two pointers, `left` and `right`, from both ends. Maintain `maxleft` and `maxright`. Calculate trapped water by `min(maxleft, maxright) - height[current]`.
Example answer:
Initialize `left=0`, `right=len(height)-1`, `maxleft=0`, `maxright=0`, `water=0`. While `left < right`, if `height[left] < height[right]`, update `maxleft` and add `maxleft - height[left]` to `water`, then `left++`. Else, update `maxright` and add `maxright - height[right]` to `water`, then `right--`. Return `water`.
7. How do you convert a fraction to its recurring decimal representation?
Why you might get asked this:
This problem assesses your handling of edge cases, integer division, and detection of repeating patterns using hash maps, a common test in Goldman Sachs LeetCode interview questions.
How to answer:
Handle sign and integer part. For the fractional part, use a hash map to store remainders and their positions. If a remainder repeats, a cycle is found.
Example answer:
Start with `num/den`. Append integer part. For remainder, multiply by 10. Store remainder and its index in a map. If remainder repeats, insert `()` at the stored index.
8. How do you find the first unique character in a string?
Why you might get asked this:
This easy problem checks basic string manipulation and hash table usage for frequency counting, a fundamental skill often assessed in Goldman Sachs LeetCode interview questions.
How to answer:
Use a hash map to store character frequencies. Then, iterate through the string again to find the first character with a frequency of one.
Example answer:
Count character frequencies using a hash map. Iterate through the string; if `char_counts[char]` is 1, return its index. If no unique character, return -1.
9. How would you design a HashMap from scratch?
Why you might get asked this:
This design problem tests your understanding of hash table internals, collision resolution, and capacity management, essential for lower-level system design in Goldman Sachs LeetCode interview questions.
How to answer:
Implement an array of linked lists (buckets) for collision handling. Define hash function, `put`, `get`, `remove` methods. Consider resizing.
Example answer:
Use an array `buckets` where each `bucket` is a list of `[key, value]` pairs. Implement `_hash(key)` to get index. `put`: iterate bucket, update/add. `get`: iterate bucket, find key. `remove`: iterate, delete.
10. How do you find the minimum number of turns to open a lock from "0000" to a target combination?
Why you might get asked this:
This medium problem tests Breadth-First Search (BFS) on a graph, where states are lock combinations. BFS is a common pattern in Goldman Sachs LeetCode interview questions for shortest path on unweighted graphs.
How to answer:
Use BFS. Start with "0000". In each step, generate all 8 possible next combinations (spin one wheel up/down). Use a queue and a visited set (including dead ends).
Example answer:
Initialize queue with ("0000", 0). Add "0000" to visited set. If "0000" is a dead end, return -1. Pop state, generate neighbors. If neighbor is target, return turns. Else, enqueue if not visited/dead end.
11. How do you find the maximum sum of a circular subarray?
Why you might get asked this:
This medium problem extends Kadane's algorithm, testing dynamic programming and handling circularity, a good challenge for Goldman Sachs LeetCode interview questions.
How to answer:
Find max subarray sum (Kadane's). Then, find min subarray sum. Max circular sum is `totalsum - minsubarray_sum`. Compare this with max non-circular sum.
Example answer:
Apply Kadane's algorithm to find `maxsofar` (normal max subarray sum). Calculate `minsofar` (min subarray sum). The circular sum is `totalsum - minsofar`. Return `max(maxsofar, circularsum)`. Handle all negatives.
12. How do you search for a target value in a rotated sorted array?
Why you might get asked this:
This problem assesses modified binary search, requiring adaptation of a fundamental algorithm. It's frequently asked in Goldman Sachs LeetCode interview questions to test logical reasoning.
How to answer:
Perform a binary search, but in each step, determine which half is sorted. Based on the target value, decide whether to search in the sorted or unsorted half.
Example answer:
Use `left`, `right` pointers. Calculate `mid`. If `nums[mid] == target`, return `mid`. Else, if `nums[left] <= nums[mid]` (left half sorted), check if target is in range `[nums[left], nums[mid])`. Adjust `left`/`right`.
13. How do you find all unique combinations of numbers that sum up to a target?
Why you might get asked this:
This medium problem tests backtracking, a recursive technique for exploring all solutions, often appearing in Goldman Sachs LeetCode interview questions for combinatorial problems.
How to answer:
Use a recursive backtracking function. Sort candidates to handle duplicates efficiently. At each step, either include the current number or skip it.
Example answer:
Define `backtrack(remain, combo, startindex)`. Base cases: `remain < 0` (invalid), `remain == 0` (add `combo` to results). Recursive step: iterate from `startindex`, `combo.append(num)`, `backtrack(remain - num, combo, i)`. `combo.pop()`.
14. How do you find the minimum number of jumps to reach the last index of an array?
Why you might get asked this:
This medium problem tests greedy algorithms or dynamic programming, focusing on optimization and efficient traversal—a key aspect of Goldman Sachs LeetCode interview questions.
How to answer:
Use a greedy approach. Maintain `currentreach` (farthest reachable index with current jumps) and `maxreach` (farthest reachable index from current position). Increment jumps when `i` exceeds `current_reach`.
Example answer:
Initialize `jumps=0`, `currentjumpend=0`, `farthest=0`. Iterate through array: `farthest = max(farthest, i + nums[i])`. If `i == currentjumpend`, increment `jumps` and update `currentjumpend = farthest`.
15. How do you generate all possible permutations of a list of distinct numbers?
Why you might get asked this:
This problem tests backtracking, a crucial recursive pattern for generating combinations and permutations. It is a common type of Goldman Sachs LeetCode interview question.
How to answer:
Use a recursive backtracking function. At each step, iterate through available numbers, add one to the current permutation, mark it as used, and recurse. Backtrack by removing it.
Example answer:
`backtrack(currentpermutation, usedmask)`: Base case: `len(current_permutation) == len(nums)`. Recursive step: iterate `i` from `0` to `len(nums)-1`. If `i` not used, `add nums[i]`, mark `used`, `backtrack()`, then `remove nums[i]`, unmark `used`.
16. How do you find the minimum path sum in a grid?
Why you might get asked this:
This medium problem involves dynamic programming on a 2D grid, a standard pattern for optimization problems. It frequently appears in Goldman Sachs LeetCode interview questions.
How to answer:
Use dynamic programming. `dp[i][j]` represents the minimum path sum to reach `(i, j)`. Fill DP table using `dp[i][j] = grid[i][j] + min(dp[i-1][j], dp[i][j-1])`. Handle base cases.
Example answer:
Create `dp` table same size as `grid`. `dp[0][0] = grid[0][0]`. Fill first row and column. For `(i,j)`, `dp[i][j] = grid[i][j] + min(dp[i-1][j], dp[i][j-1])`. Return `dp[m-1][n-1]`.
17. How many distinct ways are there to climb to the top of n stairs?
Why you might get asked this:
This easy problem is a classic dynamic programming example, often used as an introduction to the concept. It's a foundational type of Goldman Sachs LeetCode interview question.
How to answer:
This is a Fibonacci sequence variation. `dp[i]` is the number of ways to reach stair `i`. `dp[i] = dp[i-1] + dp[i-2]`. Base cases `dp[1]=1`, `dp[2]=2`.
Example answer:
If `n <= 2`, return `n`. Create `dp` array. `dp[1]=1, dp[2]=2`. Iterate `i` from 3 to `n`, `dp[i] = dp[i-1] + dp[i-2]`. Return `dp[n]`.
18. How do you merge two sorted arrays into one sorted array?
Why you might get asked this:
This easy problem tests array manipulation and two-pointer techniques, focusing on in-place modification and efficiency. It's a common warm-up in Goldman Sachs LeetCode interview questions.
How to answer:
Use a two-pointer approach, starting from the end of both arrays and placing larger elements at the end of the first array (if merging in-place).
Example answer:
Set pointers `p1` to end of `nums1` valid elements, `p2` to end of `nums2`, `p` to end of `nums1` total length. While `p1 >= 0` and `p2 >= 0`, compare `nums1[p1]` and `nums2[p2]`, place larger at `nums1[p]`, decrement respective pointers and `p`. Copy remaining `nums2` elements if any.
19. How many ways can a message containing letters from A-Z be decoded?
Why you might get asked this:
This medium problem involves dynamic programming, requiring careful handling of character combinations and edge cases (e.g., '0'). It's a good test for Goldman Sachs LeetCode interview questions.
How to answer:
Use DP. `dp[i]` is the number of ways to decode substring `s[0...i-1]`. Consider single-digit and two-digit decodings, handling '0' carefully.
Example answer:
`dp[0] = 1`, `dp[1] = 1` if `s[0] != '0'`. Iterate `i` from 2 to `n`: `dp[i] = dp[i-1]` if `s[i-1]` is valid (1-9). `dp[i] += dp[i-2]` if `s[i-2:i]` is valid (10-26). Return `dp[n]`.
20. How do you validate if a given binary tree is a valid Binary Search Tree (BST)?
Why you might get asked this:
This medium problem checks your understanding of tree traversals (DFS, in-order) and BST properties, a frequent topic in Goldman Sachs LeetCode interview questions.
How to answer:
Perform an in-order traversal. For a valid BST, the elements visited in in-order traversal should be strictly increasing. Keep track of the `prev` visited node's value.
Example answer:
`isValidBST(root, minval, maxval)`: Base case `root is None`, return true. Recursive check: `root.val > minval` and `root.val < maxval`, then recursively check left child with `(minval, root.val)` and right child with `(root.val, maxval)`.
21. How do you generate Pascal’s Triangle up to a given number of rows?
Why you might get asked this:
This easy array problem tests iterative pattern generation and basic list manipulation, serving as a good warm-up or quick check in Goldman Sachs LeetCode interview questions.
How to answer:
Generate row by row. Each number is the sum of the two numbers directly above it in the previous row. Start and end of each row are always 1.
Example answer:
Initialize `result = []`. For `i` from `0` to `numRows-1`: create `currentrow = [1]*(i+1)`. If `i > 1`, iterate `j` from `1` to `i-1`, `currentrow[j] = result[i-1][j-1] + result[i-1][j]`. Add `current_row` to `result`.
22. What is the maximum profit you can achieve by buying and selling a stock?
Why you might get asked this:
This easy problem assesses basic array iteration and finding minimums/maximums, demonstrating efficient one-pass solutions often preferred in Goldman Sachs LeetCode interview questions.
How to answer:
Iterate through prices, keeping track of the minimum price encountered so far. At each step, calculate the potential profit and update the maximum profit.
Example answer:
Initialize `minprice = infinity` and `maxprofit = 0`. Iterate through `price` in `prices`: `minprice = min(minprice, price)`. `maxprofit = max(maxprofit, price - minprice)`. Return `maxprofit`.
23. How do you copy a linked list with random pointers?
Why you might get asked this:
This medium linked list problem tests complex pointer manipulation and hash map usage to handle random connections efficiently. It's a common challenge in Goldman Sachs LeetCode interview questions.
How to answer:
Use a hash map to store `originalnode -> copiednode` mappings. Iterate once to create new nodes and populate `next` pointers, then iterate again to populate `random` pointers using the map.
Example answer:
Create a map `oldtonew` for node mapping. Iterate original list: `oldtonew[node] = Node(node.val)`. Iterate again: `oldtonew[node].next = oldtonew[node.next]`, `oldtonew[node].random = oldtonew[node.random]`. Return `oldtonew[head]`.
24. How do you detect if a linked list has a cycle?
Why you might get asked this:
This easy linked list problem tests the fast and slow pointer technique, a crucial pattern for list manipulation and a common Goldman Sachs LeetCode interview question.
How to answer:
Use two pointers, `slow` and `fast`. `slow` moves one step, `fast` moves two. If they meet, there's a cycle. If `fast` or `fast.next` becomes `None`, no cycle.
Example answer:
Initialize `slow = head`, `fast = head`. While `fast` and `fast.next`: `slow = slow.next`, `fast = fast.next.next`. If `slow == fast`, return `True`. Return `False`.
25. How do you find the next lexicographically greater permutation of numbers?
Why you might get asked this:
This medium array problem tests understanding of permutations and in-place array manipulation, requiring careful pointer logic. It's a classic Goldman Sachs LeetCode interview question.
How to answer:
Find the first decreasing element from right. Find smallest element to its right that is greater. Swap them. Reverse the subarray to the right of the swap point.
Example answer:
Find `i` such that `nums[i] < nums[i+1]` (from right). If no such `i`, reverse whole array. Find `j` such that `nums[j] > nums[i]` (from right). Swap `nums[i]` and `nums[j]`. Reverse subarray from `i+1` to end.
26. How do you generate all possible subsets of a set of distinct integers?
Why you might get asked this:
This medium problem tests backtracking or bit manipulation for combinatorial generation, a frequently asked type in Goldman Sachs LeetCode interview questions.
How to answer:
Use backtracking: for each element, decide to include it or not. Or, use bit manipulation: each bit in a counter corresponds to including/excluding an element.
Example answer:
`backtrack(index, currentsubset)`: Base case: add `currentsubset` to results. Recursive step: `currentsubset.append(nums[index])`, `backtrack(index + 1, currentsubset)`. `currentsubset.pop()`. `backtrack(index + 1, currentsubset)`.
27. How do you find the starting gas station index to complete a circular tour?
Why you might get asked this:
This medium problem tests greedy algorithms, focusing on maintaining a balance and identifying a valid starting point efficiently. It is a common Goldman Sachs LeetCode interview question.
How to answer:
Iterate, track `currenttank` and `totaltank`. If `currenttank` drops below zero, reset `currenttank` and update `startnode`. If `totaltank` is negative at end, no solution.
Example answer:
Initialize `totalgas = 0`, `currentgas = 0`, `startstation = 0`. Iterate `i` from `0` to `n-1`: `totalgas += gas[i] - cost[i]`, `currentgas += gas[i] - cost[i]`. If `currentgas < 0`, `currentgas = 0`, `startstation = i + 1`. If `totalgas < 0`, return -1. Else, return `startstation`.
28. How do you find unique frequencies of elements in an array?
Why you might get asked this:
This medium problem assesses hash map usage for frequency counting and then a hash set to check for unique frequencies. It tests two-step data structure application.
How to answer:
First, count frequencies of each number using a hash map. Second, store these frequencies in a hash set. If any frequency is already in the set, they are not unique.
Example answer:
Use a `collections.Counter` (or hash map) to get element frequencies. Then, create a `set` of these frequencies. If `len(setoffrequencies) == len(dictoffrequencies)`, return `True`, else `False`.
29. How do you find the pivot index in an array where sum of left and right halves are equal?
Why you might get asked this:
This easy array problem introduces prefix sums, an optimization technique. It's often used in Goldman Sachs LeetCode interview questions to check for efficient sum calculation.
How to answer:
Calculate the total sum of the array. Iterate through the array, maintaining a `leftsum`. The `rightsum` is `totalsum - leftsum - currentnum`. Return index if `leftsum == right_sum`.
Example answer:
Calculate `totalsum` of array. Initialize `leftsum = 0`. Iterate `i` through `nums`: `rightsum = totalsum - leftsum - nums[i]`. If `leftsum == rightsum`, return `i`. Else, `leftsum += nums[i]`. Return -1.
30. How do you generate all possible balanced parentheses for n pairs?
Why you might get asked this:
This medium problem is a classic backtracking challenge, involving constraints on building valid structures. It’s frequently asked in Goldman Sachs LeetCode interview questions.
How to answer:
Use backtracking. Maintain `opencount` and `closecount`. Only add '(' if `opencount < n`. Only add ')' if `closecount < opencount`. Base case when `opencount == n` and `close_count == n`.
Example answer:
`generate(currentstring, openc, closec)`: If `len(currentstring) == 2n`, add to result. If `openc < n`, `generate(currentstring + "(", openc + 1, closec)`. If `closec < openc`, `generate(currentstring + ")", openc, close_c + 1)`.
Other Tips to Prepare for a Goldman Sachs LeetCode Interview
Mastering Goldman Sachs LeetCode interview questions requires more than just memorizing solutions; it demands a deep understanding of core computer science principles and robust problem-solving skills. As software engineer John Sonmez once said, "The only way to do great work is to love what you do. If you haven't found it yet, keep looking. Don't settle." This applies to your preparation as well – approach it with genuine curiosity.
Beyond practicing individual problems, focus on recognizing common algorithmic patterns such as dynamic programming, greedy algorithms, backtracking, and various graph traversals. Understand the time and space complexity implications of your solutions. Crucially, practice explaining your thought process clearly and concisely, as communication is key in Goldman Sachs technical interviews. Mock interviews are invaluable for refining this skill under pressure. Consider using tools like Verve AI Interview Copilot to simulate real interview scenarios and receive instant feedback on your approach and code. Verve AI Interview Copilot can help you articulate your solutions better and identify areas for improvement. Leverage its features to refine your explanations and ensure you cover all edge cases. For further practice and detailed insights, explore resources like https://vervecopilot.com. As Benjamin Franklin advised, "By failing to prepare, you are preparing to fail." Take advantage of every tool available, including Verve AI Interview Copilot, to maximize your readiness for Goldman Sachs coding challenges.
Frequently Asked Questions Q1: How much LeetCode should I do for Goldman Sachs? A1: Aim for at least 150-200 medium to hard problems, focusing on common patterns relevant to their interview questions.
Q2: Are Goldman Sachs LeetCode questions difficult? A2: They range from easy to hard, with a strong emphasis on medium difficulty problems that test core DSA and algorithmic thinking.
Q3: What data structures are most important for Goldman Sachs LeetCode interviews? A3: Arrays, strings, hash tables, linked lists, trees (especially BSTs), and graphs are critically important.
Q4: Should I memorize solutions to Goldman Sachs LeetCode interview questions? A4: No, focus on understanding the underlying algorithms and problem-solving techniques rather than memorizing specific answers.
Q5: Is it okay to use Python for Goldman Sachs LeetCode interviews? A5: Yes, most modern companies, including Goldman Sachs, allow popular languages like Python, Java, and C++.
Q6: How long does a Goldman Sachs technical interview typically last? A6: Technical interviews usually last 45-60 minutes, with most of that time dedicated to solving 1-2 LeetCode-style problems.
Kent McAllister
Career Advisor
