Freaks City

The word chain problem involves constructing the longest possilbe sequence ("dragon") from a given set of words, starting with a specified character. Each word may be used at most twice in the chain. When two words are joined, overlapping parts are merged into one—e.g., beast and astonish form beastonish. Importantly, no word in the c ...

Problem 216: Combination Sum III Description: Given two integers k and n, find all possible combinations of k numbers from 1 to 9 that add up to n. Each number can only be used once in a combination. Approach This problem requires finding subsets of size k from the set [1,2,3,4,5,6,7,8,9] where the sum equals n. The parameter k represents the d ...

Introduction During the summer vacation, I systematically studied various operations on trees through Teacher Tuo's sharing and discovered many useful techniques, which I now summarize. Teacher Tuo is amazing! One Problem Type: Batch processing queries of the form f(dep(lca(x,y))), where f(x) is a function of x. Approach: First perform tree ...

Depth-First Search on Adjacency-Matrix Graphs void DFS(MGraph G, Vertex v, void (*visit)(Vertex)) { visit(v); Visited[v] = true; for (Vertex w = 0; w < G->Nv; ++w) if (G->G[v][w] && !Visited[w]) DFS(G, w, visit); } Breadth-First Search on Adjacency-List Graphs void BFS(LGraph G, Vertex s, void ...

Algorithmic Approach When handling graph problems, especially those involving large datasets, an adjacency list is often preferred over an adjacency matrix to optimize memory usage, particularly when the vertex count may exceed standard limits. To determine if an undirected graph is connected, one can traverse the structure using either Depth-F ...

RC-u1 Heat Wave Problem Summary: Given daily maximum temperatures and the day of the week for the first day, count how many days have temperatures ≥ 35°C. Days falling on weekends (Saturday and Sunday) should be counted separately. Solution: Iterate through the temperature data while tracking the current weekday. For each temperature ≥ 35, incr ...

Definition Search algorithms systematically explore state spaces to find optimal solutions or count valid configurations through exhaustive enumeration. This approach leverages understanding of state transitions to navigate possible states. Search Algorithm Applications When explicit enumeration becomes infeasible (e.g., permutations for n=100 ...

Problem Description Little K enjoys browsing Luogu blog articles for knowledge. Each article may have several (or none) reference links pointing to other blog articels. Little K is very curious: if he reads an article, he will certainly read its references (unless he has already read that reference). Assume there are n (n ≤ 10^5) articles on Lu ...

To retrieve node values from a binary tree in ascending order (for a BST) or the standard left-root-right sequence, a recursive approach works cleanly. The traversal explores the left subtreee first, records the current node, then visits the right subtree. Below are Python implementations that illustrate this technique. class TreeNode: def ...

Simulation problems, often labeled as "warm-up" or "signature" tasks in contests, require translating problem statements directly into code without relying on predefined algorithms. While they appear simple, their difficulty lies in accurately interpreting edge cases and constraints. A single oversight in boundary checks or ...