Language-Specific Prep
C++ Coding Interview Questions (2026)
C++ is the language of choice for competitive programmers and is widely accepted at FAANG companies. Its Standard Template Library (STL) provides ready-made data structures and algorithms that map directly to interview problems. C++ is especially strong for problems requiring manual memory management, pointer manipulation, or performance-critical code.
321 problems with C++ solutions
45 Easy 256 Medium 20 Hard
Why C++ for Coding Interviews
Strengths
- ✓STL provides ready-made data structures: vector, map, set, unordered_map, priority_queue, deque, stack, queue
- ✓The most efficient language for runtime performance
- ✓Strong typing catches many bugs at compile time
- ✓Manual memory control for advanced data structure problems
- ✓Accepted everywhere — no company rejects C++
- ✓Competitive programming standard — fastest for timed contests
Watch Out For
- ⚠Verbose syntax — more boilerplate than Python
- ⚠Manual memory management pitfalls (dangling pointers, memory leaks)
- ⚠Complex template syntax can confuse under pressure
- ⚠No built-in arbitrary-precision integers
- ⚠Pointer arithmetic errors are hard to debug in interviews
- ⚠Longer compilation times for template-heavy code
Must-Know C++ STL for Interviews
std::vector — dynamic array (push_back, pop_back, size, [])
std::unordered_map / std::unordered_set — O(1) average lookup
std::map / std::set — O(log n) sorted order
std::priority_queue — max-heap by default (use std::greater for min-heap)
std::deque — O(1) push/pop from both ends
std::sort with custom comparators
std::pair and std::tuple for grouping values
std::accumulate for summing ranges
std::memset, std::fill for array initialization
Range-based for loops: for (auto& x : vec)
C++ Interview Tips
Use unordered_map for O(1) lookup
std::unordered_map<int, int> freq; gives O(1) average insert/lookup. Use freq[x]++ for counting, freq.count(x) to check existence. For sorted iteration, use std::map instead (O(log n) per operation).
Min-heap with std::priority_queue
Default priority_queue is a max-heap. For min-heap: std::priority_queue<int, vector<int>, greater<int>> pq; For pairs: priority_queue<pair<int,int>, vector<pair<int,int>>, greater<pair<int,int>>> pq; The min element is always on top.
Use emplace_back over push_back
vec.emplace_back(args...) constructs the element in-place, avoiding a copy. For pairs: v.emplace_back(i, j) instead of v.push_back(make_pair(i, j)). Slightly faster and cleaner.
Lambdas for custom sorting
std::sort(v.begin(), v.end(), [](const auto& a, const auto& b) { return a.first > b.first; }); Lambdas are cleaner than writing a separate comparator function. Capture variables with [&] for by-reference.
Use auto to reduce type verbosity
auto x = 42; auto& ref = vec[0]; auto [key, val] = *map.begin(); Structured bindings (C++17) let you unpack pairs/tuples directly. This makes code cleaner under time pressure.
C++ Coding Interview Problems by Pattern
⊞
Sliding Window
(27) ⇄
Two Pointers
(51) ⌖
Binary Search
(34) Σ
Prefix Sum
(9)| Subarray Sum Equals K | Medium | C++ → |
| Product of Array Except Self | Medium | C++ → |
| Range Sum Query - Immutable | Easy | C++ → |
| Contiguous Array | Medium | C++ → |
| Find Pivot Index | Easy | C++ → |
| Running Sum of 1D Array | Easy | C++ → |
| Minimum Average Difference | Medium | C++ → |
| Max Chunks To Make Sorted | Medium | C++ → |
| Max Chunks To Make Sorted II | Medium | C++ → |
#
Hash Map / Set
(12)| Two Sum | Easy | C++ → |
| Group Anagrams | Medium | C++ → |
| Top K Frequent Elements | Medium | C++ → |
| Valid Anagram | Easy | C++ → |
| Longest Consecutive Sequence | Medium | C++ → |
| Contains Duplicate | Easy | C++ → |
| Word Pattern | Easy | C++ → |
| Isomorphic Strings | Easy | C++ → |
| LRU Cache | Medium | C++ → |
| 4Sum II | Medium | C++ → |
| Number of Good Pairs | Easy | C++ → |
| Subarray Sum Divisible by K | Medium | C++ → |
⬚
Stack
(22)| Valid Parentheses | Easy | C++ → |
| Min Stack | Medium | C++ → |
| Evaluate Reverse Polish Notation | Medium | C++ → |
| Daily Temperatures | Medium | C++ → |
| Decode String | Medium | C++ → |
| Asteroid Collision | Medium | C++ → |
| Remove K Digits | Medium | C++ → |
| Car Fleet | Medium | C++ → |
| Basic Calculator II | Medium | C++ → |
| Simplify Path | Medium | C++ → |
| Next Largest Element to Right | Medium | C++ → |
| Next Largest Element to Left | Medium | C++ → |
| Next Smallest Element to Left | Medium | C++ → |
| Next Smallest Element to Right | Medium | C++ → |
| Maximum Area Rectangle in Binary Matrix | Medium | C++ → |
| Minimum Element in Stack with Extra Space | Medium | C++ → |
| Minimum Element in Stack in O | Medium | C++ → |
| Implement Queue using Stack | Medium | C++ → |
| Implement Stack using Queues | Medium | C++ → |
| Remove All Occurrences of a Substring | Medium | C++ → |
| Minimum invalid parentheses to remove to make valid parentheses | Easy | C++ → |
| Minimum Add to Make Parentheses Valid | Medium | C++ → |
▷
Queue / BFS
(10)| Number of Islands | Medium | C++ → |
| Rotting Oranges | Medium | C++ → |
| Binary Tree Level Order Traversal | Medium | C++ → |
| Word Ladder | Hard | C++ → |
| 01 Matrix | Medium | C++ → |
| Walls and Gates | Medium | C++ → |
| Shortest Path in Binary Matrix | Medium | C++ → |
| Open the Lock | Medium | C++ → |
| Minimum Genetic Mutation | Medium | C++ → |
| Jump Game III | Medium | C++ → |
△
Heap / Priority Queue
(14)| Kth Largest Element in an Array | Medium | C++ → |
| Find Median from Data Stream | Hard | C++ → |
| Task Scheduler | Medium | C++ → |
| Merge K Sorted Lists | Hard | C++ → |
| K Closest Points to Origin | Medium | C++ → |
| Reorganize String | Medium | C++ → |
| Top K Frequent Words | Medium | C++ → |
| Find K Pairs with Smallest Sums | Medium | C++ → |
| Minimum Cost to Connect Sticks | Medium | C++ → |
| Sort an Almost Sorted Array | Medium | C++ → |
| Find K Closest Elements | Medium | C++ → |
| Connect Ropes to Minimize the Cost | Medium | C++ → |
| The sum of Elements between k1 smallest and k2 smallest numbers | Medium | C++ → |
| Kth Largest Element in a Stream | Medium | C++ → |
⟶
Linked List
(24)| Reverse Linked List | Easy | C++ → |
| Linked List Cycle | Easy | C++ → |
| Merge Two Sorted Lists | Easy | C++ → |
| Reorder List | Medium | C++ → |
| Add Two Numbers | Medium | C++ → |
| Remove Nth Node From End of List | Medium | C++ → |
| Copy List with Random Pointer | Medium | C++ → |
| Palindrome Linked List | Easy | C++ → |
| Swap Nodes in Pairs | Medium | C++ → |
| Rotate List | Medium | C++ → |
| Reverse Nodes in k-Group | Hard | C++ → |
| Find the intersection of two linked lists | Medium | C++ → |
| Middle of the Linked List | Easy | C++ → |
| Add Two Numbers Represented in Linked List | Medium | C++ → |
| Linked List Cycle II | Medium | C++ → |
| Remove Duplicates from Sorted List | Easy | C++ → |
| Remove Duplicates from Sorted List - II | Easy | C++ → |
| Add Two Numbers II | Medium | C++ → |
| Odd Even Linked List | Medium | C++ → |
| Reverse a Linked List in groups of given size k | Medium | C++ → |
| Reverse Linked List II | Medium | C++ → |
| Convert Binary Number in a Linked List to Integer | Medium | C++ → |
| Partition List | Medium | C++ → |
| Sort List | Medium | C++ → |
🌲
Trees / DFS
(18) ◉
Graphs
(10)| Clone Graph | Medium | C++ → |
| Pacific Atlantic Water Flow | Medium | C++ → |
| Number of Connected Components in Undirected Graph | Medium | C++ → |
| Surrounded Regions | Medium | C++ → |
| Minimum Height Trees | Medium | C++ → |
| Network Delay Time | Medium | C++ → |
| Find Eventual Safe States | Medium | C++ → |
| All Paths From Source to Target | Medium | C++ → |
| Cheapest Flights Within K Stops | Medium | C++ → |
| Graph Valid Tree | Medium | C++ → |
◫
Dynamic Programming
(26)| Climbing Stairs | Easy | C++ → |
| House Robber | Medium | C++ → |
| Coin Change | Medium | C++ → |
| Longest Increasing Subsequence | Medium | C++ → |
| Longest Common Subsequence | Medium | C++ → |
| Word Break | Medium | C++ → |
| Edit Distance | Hard | C++ → |
| Unique Paths | Medium | C++ → |
| Maximum Subarray | Medium | C++ → |
| Decode Ways | Medium | C++ → |
| Min Cost Climbing Stairs | Easy | C++ → |
| House Robber II | Medium | C++ → |
| Partition Equal Subset Sum | Medium | C++ → |
| Target Sum | Medium | C++ → |
| Best Time to Buy and Sell Stock | Easy | C++ → |
| Palindromic Substrings | Medium | C++ → |
| Longest Palindromic Substring | Medium | C++ → |
| Best Time to Buy and Sell Stock with Cooldown | Medium | C++ → |
| Maximum Product Subarray | Medium | C++ → |
| Triangle | Medium | C++ → |
| Minimum Path Sum | Medium | C++ → |
| Perfect Squares | Medium | C++ → |
| Regular Expression Matching | Hard | C++ → |
| Interleaving String | Medium | C++ → |
| Best Time to Buy and Sell Stock with Transaction Fee | Medium | C++ → |
| Integer Break | Medium | C++ → |
◈
Greedy
(8)| Jump Game | Medium | C++ → |
| Jump Game II | Medium | C++ → |
| Gas Station | Medium | C++ → |
| Non-overlapping Intervals | Medium | C++ → |
| Meeting Rooms II | Medium | C++ → |
| Queue Reconstruction by Height | Medium | C++ → |
| Minimum Number of Arrows to Burst Balloons | Medium | C++ → |
| Candy | Hard | C++ → |
↩
Backtracking
(14)| Permutations | Medium | C++ → |
| Subsets | Medium | C++ → |
| Combination Sum | Medium | C++ → |
| Word Search | Medium | C++ → |
| Letter Combinations of a Phone Number | Medium | C++ → |
| Generate Parentheses | Medium | C++ → |
| N-Queens | Hard | C++ → |
| Palindrome Partitioning | Medium | C++ → |
| Combination Sum II | Medium | C++ → |
| Subsets II | Medium | C++ → |
| Next Permutation | Medium | C++ → |
| Find all permutations of a string | Medium | C++ → |
| Find all permutations of a given string without duplicates | Medium | C++ → |
| Longest Valid Parentheses | Easy | C++ → |
T
Trie
(5)| Implement Trie (Prefix Tree) | Medium | C++ → |
| Design Add and Search Words Data Structure | Medium | C++ → |
| Word Search II | Hard | C++ → |
| Longest Word in Dictionary | Medium | C++ → |
| Replace Words | Medium | C++ → |
∪
Union Find
(6)| Redundant Connection | Medium | C++ → |
| Accounts Merge | Medium | C++ → |
| Number of Provinces | Medium | C++ → |
| Satisfiability of Equality Equations | Medium | C++ → |
| Swim in Rising Water | Hard | C++ → |
| Most Stones Removed with Same Row or Column | Medium | C++ → |
↗
Monotonic Stack
(7)| Largest Rectangle in Histogram | Hard | C++ → |
| Next Greater Element I | Easy | C++ → |
| Sum of Subarray Minimums | Medium | C++ → |
| Online Stock Span | Medium | C++ → |
| 132 Pattern | Medium | C++ → |
| Remove Duplicate Letters | Medium | C++ → |
| Stock Span Problem | Medium | C++ → |
→
Topological Sort
(5)| Course Schedule | Medium | C++ → |
| Course Schedule II | Medium | C++ → |
| Parallel Courses | Medium | C++ → |
| Sequence Reconstruction | Medium | C++ → |
| Alien Dictionary | Hard | C++ → |
&
Bit Manipulation
(8)| Single Number | Easy | C++ → |
| Missing Number | Easy | C++ → |
| Counting Bits | Easy | C++ → |
| Number of 1 Bits | Easy | C++ → |
| Reverse Bits | Easy | C++ → |
| Sum of Two Integers | Medium | C++ → |
| Single Number II | Medium | C++ → |
| Power of Two | Easy | C++ → |
⊣⊢
Intervals
(4)| Merge Intervals | Medium | C++ → |
| Insert Interval | Medium | C++ → |
| Minimum Interval to Include Each Query | Hard | C++ → |
| Meeting Rooms | Easy | C++ → |
⊠
Matrix
(7)| Rotate Image | Medium | C++ → |
| Spiral Matrix | Medium | C++ → |
| Set Matrix Zeroes | Medium | C++ → |
| Maximal Square | Medium | C++ → |
| Game of Life | Medium | C++ → |
| Search a 2D Matrix II | Medium | C++ → |
| Count Negative Numbers in a Sorted Matrix | Easy | C++ → |
Frequently Asked Questions
Is C++ good for coding interviews?
Yes — C++ is one of the best languages for coding interviews, especially if you know the STL well. It is accepted at every company and is the standard for competitive programming. The STL provides ready-made data structures (vector, map, set, priority_queue) that map directly to interview problems. The main trade-off is verbosity compared to Python.
What STL containers should I know for coding interviews?
The essential STL containers for interviews: vector (dynamic array), unordered_map/unordered_set (O(1) hash lookup), map/set (O(log n) sorted), priority_queue (heap), deque (double-ended queue), stack, and queue. Master these 8 containers and you can solve any interview problem in C++.
How do I create a min-heap in C++?
Use std::priority_queue with std::greater: std::priority_queue<int, std::vector<int>, std::greater<int>> minHeap; The top() element is the minimum. For pairs: std::priority_queue<std::pair<int,int>, std::vector<std::pair<int,int>>, std::greater<std::pair<int,int>>> pq;
Should I use C++ or Python for coding interviews?
Use C++ if you are targeting competitive programming, game development, systems engineering, or HFT firms. Use Python for general software engineering interviews at FAANG. C++ is faster at runtime but the extra verbosity costs time. Most interviewers care about algorithmic correctness, not language performance.
Ready to start practicing?
Browse all problems with C++ solutions, or follow the pattern-based roadmap.