Google Coding Interview Questions: Patterns and Top Problems
Preparing for Google with a generic problem list wastes weeks on questions Google rarely asks. This page fixes that. It ranks the coding questions that appear most often in Google’s tagged problem data. Each row links to a pattern guide on this site. The tables near the end turn that data into a study order.
Google’s loop is long. The coding bar stays high in every round. Pattern coverage matters more than raw problem count. A few hundred well-chosen problems, reviewed many times, are worth more than a thousand solved once.
The short version
- Mediums are about half of tagged problems at 51 percent. Easy questions open many rounds at 34 percent.
- Arrays touch 52 percent of tagged problems. Hash tables sit at 21 percent and strings sit at 20 percent.
- The bank rewards clean basics plus Hard readiness. Hard problems hold 16 percent of the set.
Google’s Interview Loop
- A recruiter call covers your background and timeline.
- One or two technical phone screens follow. Each screen has one or two coding problems.
- The onsite loop runs several rounds in one day. Most rounds are coding.
- Senior roles add system design rounds.
- A behavioral round closes the day. It asks about how you work with other people.
- Coding usually happens in a plain document. There is no autocomplete and no compiler.
That last point causes more failures than difficulty does. If you always write code inside an IDE, autocomplete does some of your work. You will not get that help at Google. Part of preparation is writing code by hand and making it correct the first time.
The Questions Google Asks Most
LeetCode tags problems by company. The tags come from candidate reports. Each tagged problem gets a relative frequency score from 0 to 100. These 20 have the highest scores for Google. Each row links to the pattern guide on this site that teaches the technique behind the problem. Practice the method, not one answer. Work down the table from top to bottom. The order moves from easy to hard.
If you learn five guides first, learn these
- Start with hash table . It covers four rows, from Two Sum to Valid Anagram.
- Take two pointers alongside it for the 3Sum and Trapping Rain Water rows.
- Learn array manipulation next. Arrays touch 52 percent of tagged problems.
- Bring in string manipulation for Longest Common Prefix. Strings sit at 20 percent of tagged problems.
- Finish with binary search . Median of Two Sorted Arrays and Sqrt(x) both need it.
| Problem | Difficulty | Demand | Pattern Guide |
|---|---|---|---|
| Two Sum | Easy | Very high | Hash Table |
| Add Two Numbers | Medium | Very high | Linked List |
| Palindrome Number | Easy | Very high | Math Algorithms |
| 3Sum | Medium | Very high | Two Pointers |
| Trapping Rain Water | Hard | Very high | Two Pointers |
| Longest Substring Without Repeating Characters | Medium | High | Sliding Window |
| Median of Two Sorted Arrays | Hard | High | Binary Search |
| Best Time to Buy and Sell Stock | Easy | High | Kadane’s Algorithm |
| Longest Common Prefix | Easy | High | String Manipulation |
| Concatenation of Array | Easy | High | Array Manipulation |
| Reverse Integer | Medium | High | Math Algorithms |
| Container With Most Water | Medium | High | Two Pointers |
| Longest Consecutive Sequence | Medium | High | Hash Table |
| Majority Element | Easy | High | Hash Table |
| Remove Duplicates from Sorted Array | Easy | High | Two Pointers |
| Valid Parentheses | Easy | High | Stack |
| Longest Palindromic Substring | Medium | High | Two Pointers |
| Valid Anagram | Easy | High | Hash Table |
| Subarray Sum Equals K | Medium | High | Prefix Sum |
| Sqrt(x) | Easy | High | Binary Search |
Most entries in this list look ordinary. Two Sum and Valid Anagram sit next to Trapping Rain Water and Median of Two Sorted Arrays. That mix is the lesson. Google tests basic skill under time pressure as much as it tests hard problems. A clean Easy solution with clear communication still passes candidates.
Topics and Difficulty at Google
Across all tagged problems, these topics appear most often. The share is the percent of tagged problems that carry the topic. One problem can carry several topics, so the shares add to more than 100 percent.
| Topic | Tagged Problems | Share |
|---|---|---|
| Array Manipulation | 258 | ~52% |
| Hash Table | 102 | ~21% |
| String Manipulation | 101 | ~20% |
| Dynamic Programming | 84 | ~17% |
| Math Algorithms | 73 | ~15% |
| Sorting | 69 | ~14% |
| Two Pointers | 61 | ~12% |
| Binary Search | 59 | ~12% |
| Graph Traversal (DFS and BFS) | 49 | ~10% |
| Greedy Algorithms | 40 | ~8% |
Sorting has no link because we treat it as part of other patterns, not as a pattern of its own. The array manipulation guide covers it. Arrays, hashing, and strings lead this table for a simple reason. Nearly three of every four tagged problems use at least one of them. Dynamic programming is next. It appears in about one tagged problem in six, so you cannot skip it. But do not study it before you finish the array and string work.
The difficulty mix backs this up. Among recently tagged Google problems:
| Difficulty | Problems | Share |
|---|---|---|
Easy | 167 | 34% |
Medium | 252 | 51% |
Hard | 77 | 16% |
Mediums are half of this list. Give them about half of your practice time. Easy questions still deserve practice. They often start an interview round, and a fast clean solution counts there. Hard questions help you stand out in onsite rounds. Do not start your preparation with them.
Method: the top 20 rows come from LeetCode company-tagged lists for Google, ranked by relative frequency scores from 0 to 100. Shares overlap because one problem can carry several topics.
Where to Spend Your Prep Time
The topic mix gives a concrete way to divide your time.
- Build the array and hash base first. About half of tagged Google problems use arrays. A hash table also turns many brute force solutions into fast ones. The hash table and array manipulation guides teach these techniques.
- Practice sliding window and two pointers in the same week. They share mechanics, and Google tests both often. Switching between them forces you to decide which one fits. That decision is a large part of the interview.
- Learn dynamic programming through standard problems. Buy-and-sell stock and longest palindromic substring cover most of what Google asks. Start with dynamic programming after the easier patterns feel safe.
- Practice without autocomplete every week. Their coding tool does not correct your mistakes. Write one solution per session in a plain editor. Check it against edge cases by hand.
- Review on a schedule. Rereading notes feels useful but keeps very little in memory. Spaced repetition shows you each problem again just before you forget it.
graph TD
A["Array and hash base"] --> B["Sliding window and two pointers"]
B --> C["Dynamic programming basics"]
C --> D["Plain-editor practice without autocomplete"]
D --> E["Top 20 solved once"]
E --> F["Spaced repetition until interview day"]
The diagram follows the prep plan from base patterns through hand-written practice to scheduled review.
Questions Candidates Ask
Do Easy problems really matter at Google?
Yes. Easy questions hold 34 percent of tagged problems. They often start a round, where a fast clean solution counts.
Can I skip dynamic programming?
No. It appears in about one tagged problem in six at 17 percent. Start with dynamic programming after the array and string work feels safe.
Where should I start?
Start with the hash table and array manipulation guides. Arrays touch 52 percent of tagged problems. A hash table also turns many brute force solutions into fast ones.
How do I prepare for writing code without an IDE?
Write one solution per session in a plain editor. Check it against edge cases by hand. Their coding tool does not correct your mistakes.
Next Steps
Work through the top 20 table with the linked pattern guides open. Read the full concept page for every pattern you cannot explain in one minute. The coding patterns index lists all of them. Start with two pointers and sliding window . They match Google’s topic mix best. Interviewing with other companies too? See how the Amazon , Meta , and Apple guides differ on topic weight, difficulty, and pace.