Mastering Data Structures and Algorithms (DSA) is crucial for solving complex problems in coding interviews and competitive programming. One of the most effective approaches is by recognizing common patterns that repeatedly appear across various problems.
In this blog, we’ll explore 15 essential DSA patterns, provide explanations, common problems, and direct links to practice resources. Let’s dive in! 🧠💻
🧮 1. Prefix Sum Pattern
Use this to efficiently compute subarray sums using preprocessed cumulative sums.
🔍 Common Use Cases:
- Sum of all subarrays of size
k - Range sum queries
- Subarray sum equals a given target
👫 2. Two Pointers Pattern
Optimize traversal in sorted arrays or linked lists using two pointers moving towards or away from each other.
🔍 Common Use Cases:
- Pair with a given sum
- Remove duplicates
- Find middle of a linked list
🪟 3. Sliding Window Pattern
Great for problems involving contiguous subarrays or substrings using a dynamic window.
🔍 Common Use Cases:
- Max sum subarray of size
k - Longest substring without repeating characters
- Minimum window substring
🐢🐇 4. Fast & Slow Pointers
Also known as the Tortoise and Hare algorithm, great for cycle detection and middle node finding.
🔍 Common Use Cases:
- Detect cycles in a linked list
- Find the middle element
- Cycle length
🔄 5. LinkedList In-place Reversal
Reverse a linked list without extra space – a must-know technique.
🔍 Common Use Cases:
- Reverse singly linked list
- Reverse
knodes - Reverse in groups
📐 6. Monotonic Stack
Solve problems involving next greater/smaller elements by maintaining a stack in sorted order.
🔍 Common Use Cases:
- Next Greater Element
- Largest Rectangle in Histogram
- Trapping Rain Water
🔝 7. Top ‘K’ Elements
Use heaps or sorting to get the most/least frequent or extreme values.
🔍 Common Use Cases:
- K largest/smallest elements
- Kth largest element
- Top
kfrequent elements
🧩 8. Overlapping Intervals
Merge or check for conflicts between intervals – crucial in calendar & scheduling apps.
🔍 Common Use Cases:
- Merge overlapping intervals
- Insert & merge new interval
- Cover range with intervals
🧭 9. Modified Binary Search
Adapt binary search for problems like search in rotated arrays or first/last occurrence.
🔍 Common Use Cases:
- Square root calculation
- Search in rotated sorted array
- First or last index in sorted array
🌲 10. Binary Tree Traversal
Master DFS-based traversals: in-order, pre-order, post-order – key for understanding trees.
🔍 Common Use Cases:
- Tree traversal techniques
- Height of a binary tree
- Level order traversal
🧗 11. Depth-First Search (DFS)
Recursively or iteratively explore deep paths – essential for graphs, backtracking, and connectivity.
🔍 Common Use Cases:
- Find all paths between nodes
- Detect cycles in graphs
- Topological sort
📶 12. Breadth-First Search (BFS)
Explore level by level, ideal for shortest path in unweighted graphs or level-order tree traversals.
🔍 Common Use Cases:
- Shortest path in graph
- Level-order traversal
- Find connected components
🗺️ 13. Matrix Traversal
Navigate through 2D grids for patterns or path-finding.
🔍 Common Use Cases:
- Spiral traversal
- Search in 2D matrix
- Largest region of 1s
🔙 14. Backtracking
Try, backtrack, and try again. Perfect for problems where multiple combinations or permutations are possible.
🔍 Common Use Cases:
- N-Queens
- Generate permutations/subsets
- Subset sum problems
📚 15. Dynamic Programming (DP)
Store and reuse subproblem results for optimal solutions – a high-yield interview pattern!
🔍 Common Use Cases:
- 0/1 Knapsack
- Longest common subsequence
- Matrix chain multiplication
🎯 Conclusion
Mastering these 15 DSA patterns will level up your problem-solving skills, help you crack interviews, and ace competitive coding rounds. Practice each one, internalize the logic, and soon you'll recognize them even in the trickiest problems.
💪 Keep learning, keep building. Happy coding!
Top comments (0)