---
title: "Alex Mateo (@alexmateo) | Hashnode"
description: "Software Engineer from Madrid, Spain. Founder of Expora. Read the latest articles by Alex Mateo on Hashnode."
url: "https://hashnode.com/@alexmateo"
---

@alexmateo

# Alex Mateo

@alexmateo · Madrid, Spain · Joined May 2026

Software Engineer from Madrid, Spain. Founder of Expora.

### [N-Queens Is Just Subsets With One Extra Line](https://alexmateo.hashnode.dev/n-queens-is-just-subsets-with-one-extra-line?utm_source=hashnode&utm_medium=feed)

N-Queens, Sudoku and subsets are the same backtracking template. The only difference is one pruning line, and here's how to see it.

4 min read · [alexmateo.hashnode.dev](https://alexmateo.hashnode.dev/n-queens-is-just-subsets-with-one-extra-line?utm_source=hashnode&utm_medium=feed)

[Jul 1](https://hashnode.com/posts/n-queens-is-just-subsets-with-one-extra-line/6a44e9a744e24959d0637eea)

### [You Learned the 7 Patterns. The Hard Problems Combine Them.](https://alexmateo.hashnode.dev/you-learned-the-7-patterns-the-hard-problems-combine-them?utm_source=hashnode&utm_medium=feed)

You drilled the 7 patterns. Real interviews stack two at a time. Here's how to see the layers.

7 min read · [alexmateo.hashnode.dev](https://alexmateo.hashnode.dev/you-learned-the-7-patterns-the-hard-problems-combine-them?utm_source=hashnode&utm_medium=feed)

[Jun 22](https://hashnode.com/posts/you-learned-the-7-patterns-the-hard-problems-combine-them/6a38fc5d93daa5b20660df74)

### [I Solved 100 LeetCode Problems Before I Realized I Was Studying the Wrong Thing](https://alexmateo.hashnode.dev/i-solved-100-leetcode-problems-before-i-realized-i-was-studying-the-wrong-thing?utm_source=hashnode&utm_medium=feed)

Solving 100 problems teaches execution, not recognition. Here's the practice shift that builds the skill interviews actually test.

8 min read · [alexmateo.hashnode.dev](https://alexmateo.hashnode.dev/i-solved-100-leetcode-problems-before-i-realized-i-was-studying-the-wrong-thing?utm_source=hashnode&utm_medium=feed)

[Jun 9](https://hashnode.com/posts/i-solved-100-leetcode-problems-before-i-realized-i-was-studying-the-wrong-thing/6a27d4d598a0b16299d20b48)

### [How to Derive Any DP Table From Scratch (Without Memorizing Solutions)](https://alexmateo.hashnode.dev/how-to-derive-any-dp-table-from-scratch-without-memorizing-solutions?utm_source=hashnode&utm_medium=feed)

Stop memorizing DP solutions. Learn the 5-step derivation process that works on any problem, including ones you have never seen before.

9 min read · [alexmateo.hashnode.dev](https://alexmateo.hashnode.dev/how-to-derive-any-dp-table-from-scratch-without-memorizing-solutions?utm_source=hashnode&utm_medium=feed)

[Jun 8](https://hashnode.com/posts/how-to-derive-any-dp-table-from-scratch-without-memorizing-solutions/6a268b118a07d1ee69aa6057)

### [Graph Algorithms for Coding Interviews: When to Use BFS, DFS, or Dijkstra](https://alexmateo.hashnode.dev/graph-algorithms-for-coding-interviews-when-to-use-bfs-dfs-or-dijkstra?utm_source=hashnode&utm_medium=feed)

Learn when to use BFS, DFS, or Dijkstra in coding interviews. Decision framework, complexity, and classic problems for each algorithm.

11 min read · [alexmateo.hashnode.dev](https://alexmateo.hashnode.dev/graph-algorithms-for-coding-interviews-when-to-use-bfs-dfs-or-dijkstra?utm_source=hashnode&utm_medium=feed)

[May 10](https://hashnode.com/posts/graph-algorithms-for-coding-interviews-when-to-use-bfs-dfs-or-dijkstra/6a004c68e3eebc2e20584ea5)