Algorithmic Solutions for Dynamic Programming and String Manipulation

Calculating Dice Roll CombinationsGiven d identical dice, each with f faces labeled from 1 to f, the objective is to determine the number of ways to achieve a specific sum target when rolling all dice. The result should be returned modulo 10^9 + 7.A recursive approach with memoization efficiently solves this by breaking the problem down into sm ...

Posted on Sun, 20 Sep 2026 16:15:08 +0000 by Floodboy

20240125 Construction Problem Solutions

P1734E First, analyze the second condition: rearrange it to $a_{r_1, c_1} - a_{r_1, c_2} \not\equiv a_{r_2, c_1} - a_{r_2, c_2} \pmod{n}$. Our goal is to ensure that the column-wise difference values between any two rows are distinct. We have not yet addressed conditions 1 and 3. Conddition 1 can be satisfied by taking all elements modulo $n$. ...

Posted on Mon, 14 Sep 2026 16:27:32 +0000 by Robkid

Virtual Judge Problem Set Solutions

A. Grid Ice Floor This problem requires analyzing the accessible states of each cell on a grid. When standing at position (i, j), there are exactly 5 possible movement states: Moving upward Moving downward Moving leftward Moving rightward Standing still We define dp[i][j][state] to indicate whether reaching cell (i, j) with a specific state i ...

Posted on Sun, 13 Sep 2026 16:14:50 +0000 by stringfield

Implementing Minimum Spanning Trees with Prim's and Kruskal's Algorithms

This document explores the implementation of algorithms to find the Minimum Spanning Tree (MST) for a given set of connected, undirected graph problems. Prim's Algorithm for Danse Graphs Prim's algorithm is efficient for dense graphs. Its complexity is O(V^2) using an adjacency matrix or O(V log V + E) with an adjacency list and a priority queu ...

Posted on Tue, 08 Sep 2026 16:17:32 +0000 by greggustin

Calculating Network Delay Time with Dijkstra and Floyd-Warshall Algorithms

Dijkstra's Algorithm ApproachDijkstra's algorithm is suitable for finding the shortest paths from a single source node to all other nodes in a weighted graph with non-negative weights. For the network delay problem, we aim to determine the maximum shortest-path distance from the source node k to every other node. If any node remains unreachable ...

Posted on Mon, 07 Sep 2026 16:54:29 +0000 by mindfield

Understanding Graph Data Structures: Adjacency Matrix and Adjacency List Representations

A graph is a data structure consisting of a set of vertices (nodes) and a set of edges that define the relationships between these vertices. Mathematically, a graph G is represented as G = (V, E), where: V is a finite, non-empty set of vertices. E is a finite set of relationships between vertices. For an undirected graph, an edge is represente ...

Posted on Wed, 02 Sep 2026 16:46:28 +0000 by GoodCoffee

Competitive Programming Techniques and Problem Analysis

Codeforces 1017D - Binary String Query Complexity: $\mathcal{O}((4^n+q) \log n)$ Distinct binary strings are limited to $2^n$. Precomputing distances between pairs allows for binary search queries. Codeforces 1080F - Colorful Graph Approach: Persistent Segment Tree / Sweep Line Treat this as a data structure challenge. By sweeping the right end ...

Posted on Fri, 28 Aug 2026 16:14:17 +0000 by CodeMama

Counting and Graph Theory Problem Solutions: Edge Inclusion-Exclusion and MST with Boruvka

Let's consider the calculation for the number of four-vertex subgraphs with at least x specific edges, denoted as f_x. Using the principle of inclusion-exclusion, the count of subgraphs with no edges at all is f_0 - f_1 + f_2 - f_3 + f_4 - f_5 + f_6. Meanwhile, the count of subgraphs with all six edges present is simply f_6. The difference we n ...

Posted on Fri, 21 Aug 2026 16:31:31 +0000 by Sfoot

Competitive Programming Contest Solutions and Analysis

Calculating Paths in Dynamic Graphs To determine the total number of simple paths in a Directed Acyclic Graph (DAG), we analyze the in-degrees and out-degrees. Let $fwd_dp[i]$ be the number of paths ending at node $i$. This can be computed using topological sorting. The total number of paths in the original graph is $\sum fwd_dp[i]$ for all nod ...

Posted on Wed, 19 Aug 2026 16:43:01 +0000 by Niccaman

Comprehensive Problem Solutions from Paken Camp Contests

2023 Edition Day 1 G. Constructing an MST with Product Weights (Easy) We are given a sequence (a) (with (|a_i| \le 10^6)), and we must build an undirected graph on (n) vertices ((n \le 2\cdot 10^5)) where the weight of edge ((i,j)) equals (a_i a_j). The goal is to compute the weight of the minimum spanning tree. First, sort (a); this has no eff ...

Posted on Fri, 14 Aug 2026 16:32:06 +0000 by Chinese