This page collects links to detailed notes on all the major problem types encountered in contests, especially AtCoder. Each link leads to a page covering the topic's theory, patterns, solution techniques, and curated practice problems.
Each topic note contains:
The Meet-in-the-Middle (MITM) technique is a problem-solving strategy commonly used to reduce the time complexity of brute-force solutions by dividing a problem into two smaller subproblems. It is particularly useful when the size of the problem is too large to solve directly using brute force, but splitting it into two halves can make it computationally feasible:
| Problem | Data Structure / Algo | 🔥 Key Insight / Mark |
|---|---|---|
| Tree Diameter | BFS | ⭐🛠️🔥 |
| Subtree Size | DFS | ⭐🛠️🔥 |
0-1 BFS is a variation of the Breadth-First-Search(BFS) algorithm, optimized for graphs where edge weights are either 0 or 1. This optimization takes advantage of the deque data structure to achieve faster performance compared to standard BFS or Dijkstra's algorithm
A bipartite graph is a type of graph where the set of vertices can be divided into two disjoint sets and such that:
Given a string S, the task is to find the longest substring which is a palindrome. If there are multiple answers, then return the first appearing substring
Examples:
forgeeksskeegforgeeksskeeg