The Art of Problem Solving: 700+ DSA Problems Later

After solving over 700 problems on LeetCode and other platforms, I've learned that success in DSA isn't about memorizing solutions—it's about developing a problem-solving mindset.

The Pattern Recognition Game

Most problems fall into recognizable patterns:

1. Two Pointers: Sorted arrays, finding pairs
2. Sliding Window: Subarray/substring problems
3. Dynamic Programming: Optimization, counting paths
4. Graph Traversal: BFS/DFS applications
5. Binary Search: Sorted data, optimization

My Problem-Solving Framework

Step 1: Understand the Problem

• Read the problem twice
• Identify inputs and outputs
• Note constraints
• Think of edge cases

Step 2: Pattern Recognition

Ask yourself:

• Is the data sorted? → Consider binary search
• Need to find a pair/triplet? → Consider two pointers
• Optimization problem? → Consider DP or greedy
• Connected components? → Consider graph traversal

Step 3: Work Through Examples

Input: nums = [2, 7, 11, 15], target = 9
Expected: [0, 1] (because 2 + 7 = 9)

Approach: Use a hash map to store complements
- For each number, check if (target - num) exists in map

The Two Sum Evolution

The famous "Two Sum" problem teaches us a lot about optimization:

Brute Force O(n²)

java
1for (int i = 0; i < n; i++) {
2    for (int j = i + 1; j < n; j++) {
3        if (nums[i] + nums[j] == target) return new int[]{i, j};
4    }
5}

Optimized O(n)

java
1Map<Integer, Integer> map = new HashMap<>();
2for (int i = 0; i < n; i++) {
3    int complement = target - nums[i];
4    if (map.containsKey(complement)) {
5        return new int[]{map.get(complement), i};
6    }
7    map.put(nums[i], i);
8}

Consistency Over Intensity

The key to improvement is consistent practice:

• Solve 2-3 problems daily
• Review solutions even when you solve them
• Learn from others' approaches
• Practice explaining your solutions

Conclusion

Problem-solving is a skill that improves with deliberate practice. The goal isn't to solve every problem perfectly on the first try—it's to build intuition and pattern recognition over time.