Solutions to ARC143 Problems: Three Integers, Counting Grids, and Piles of Pebbles
T1 Three Integers
Problem Statement
Given three integers A, B, and C, there are two operations:
Operation 1: Choose two numbers and decrement each by 1.
Operation 2: Choose all three numbers and decrement each by 1.
The goal is to reduce all three numbers to 0. If impossible, output -1.
Solution Approach
A key insight is that any operation sh ...
Posted on Sun, 20 Sep 2026 16:12:21 +0000 by evlive
AGC022F Checkers: A Dynamic Programming Approach on Multi-way Trees
We examine the problem of merging \(n\) initial unit vectors \(\mathbf{e}_1,\ldots,\mathbf{e}_n\) via operations that combine two vectors \(\mathbf{u},\mathbf{v}\) into either \(2\mathbf{u} - \mathbf{v}\) or \(2\mathbf{v} - \mathbf{u}\), depending on which one "wins". Each final vector’s \(i\)-th component is of the form \((-1)^{c_i}2 ...
Posted on Tue, 15 Sep 2026 16:36:04 +0000 by cneale
Dynamic Programming Optimization Techniques and Problem Analysis
Optimization Approaches
State Reduction: Leverage problem properties to minimize state space
Model Adaptation: Apply known algorithmic patterns to improve transition efficiency
Contribution Decomposition: Use data structures to manage partial contributions
Standard Optimizations: Utilize techniques like monotonicity, convex optimization, or sl ...
Posted on Sun, 13 Sep 2026 16:18:26 +0000 by pdn
SMU Summer 2023 Programming Contest: Solutions
This document provides solutions for problems from the SMU Summer 2023 Contest, Round 6.
A. Burger Optimization
This problem involves maximizing profit from selling two types of burgers with different ingredients and prices, given a limited number of buns. The strategy is to iterate through all possible counts of the first burger type, up to th ...
Posted on Sat, 12 Sep 2026 16:45:31 +0000 by ccx004
Calculating the Sum of Squared Binomial Coefficients
Problem DefinitionThe task involves processing multiple queries where, for a given integer n, we must compute the sum of squared binomial coefficients: $\sum_{i=0}^{n} \binom{n}{i}^2$. The result should be returned modulo $10^9 + 7$. Constraints allow for n up to $10^6$, necessitating an efficient algorithm.Naive Approach: Dynamic ProgrammingFo ...
Posted on Sat, 12 Sep 2026 16:44:55 +0000 by nogginj
Prufer Sequences
Tree to Prufer Sequence
Find the leaf node with the smallest label, and add its parent to the sequence.
Delete that leaf node.
Repeat the above operations until a sequence of length (n-2) is obtained.
The reverse process reconstructs the tree.
A Prufer sequence establishes a bijection between the spanning trees of a complete graph with (n) ve ...
Posted on Sun, 06 Sep 2026 16:21:39 +0000 by mr. big
Minimum Cowphabet Sing-throughs for an Observed String
A cow's language, known as Cowphabet, consists of the 26 lowercase letters. However, the order in which a cow recites these letters is a permutation of the standard alphabet sequence. Bessie repeats this song, and Farmer John notes down a string of letters he remembers hearing. The task is to determine the minimum number of complete Cowphabet r ...
Posted on Sun, 06 Sep 2026 16:17:46 +0000 by Bit343
: "Four Algorithmic Challenges: Month Cycles, String Formatting, Constrained Reductions, and Random Walk Probabilities"
Month Transition Calculation
Problem Statement
Given an integer current_month representing a month (1 through 12), compute the subsequent month in the annual cycle.
Solution Approach
Months follow a cyclic pattern with base 12. Converting to zero-based indexing simplifies modular arithmetic.
Implementation
def calculate_next_month(m: int) -> ...
Posted on Sun, 30 Aug 2026 16:10:57 +0000 by klpang
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
Educational Codeforces Round 157 Div. 2: Virtual Contest Analysis
Problem A: Treasure Chest
We need to calculate the minimum time to reach the chest and return to the start, given the ability to pull the chest towards the key for a maximum distance of k. There are two scenarios based on the relative positions of the chest pos_chest and the key pos_key:
If pos_key <= pos_chest: We pickup the key on the way ...
Posted on Mon, 17 Aug 2026 16:45:03 +0000 by vicodin