ICPC 2011 - F. Machine Works
State the problem in your own words. Focus on the mathematical or algorithmic core rather than repeating the full statement.
Source-first archive entry
This page is built from the copied files in competitive_programming/icpc/2011/F-machine-works. Edit
competitive_programming/icpc/2011/F-machine-works/solution.tex to update the written solution and
competitive_programming/icpc/2011/F-machine-works/solution.cpp to update the implementation.
The website does not replace those files with hand-maintained HTML. It reads the copied source tree during the build and exposes the exact files below.
Problem Statement
Copied statement text kept beside the solution archive for direct reference.
Problem F
Machine Works
Problem ID: works
You are the director of Arbitrarily Complex Machines (ACM for short), a company producing advanced machinery
using even more advanced machinery. The old production machinery has broken down, so you need to buy new
production machines for the company. Your goal is to make as much money as possible during the restructuring
period. During this period you will be able to buy and sell machines and operate them for profit while ACM owns
them. Due to space restrictions, ACM can own at most one machine at a time.
During the restructuring period, there will be several machines for sale. Being an expert in the advanced machines
market, you already know the price Pi and the availability day Di for each machines Mi . Note that if you do not buy
machine Mi on day Di , then somebody else will buy it and it will not be available later. Needless to say, you cannot
buy a machine if ACM has less money than the price of the machine.
If you buy a machine Mi on day Di , then ACM can operate it starting on day Di + 1. Each day that the machine
operates, it produces a profit of Gi dollars for the company.
You may decide to sell a machine to reclaim a part of its purchase price any day after you’ve bought it. Each machine
has a resale price Ri for which it may be resold to the market. You cannot operate a machine on the day that you sell
it, but you may sell a machine and use the proceeds to buy a new machine on the same day.
Once the restructuring period ends, ACM will sell any machine that it still owns. Your task is to maximize the amount
of money that ACM makes during the restructuring.
Input
The input consists of several test cases. Each test case starts with a line containing three positive integers N , C, and
D. N is the number of machines for sale (N ≤ 105 ), C is the number of dollars with which the company begins the
restructuring (C ≤ 109 ), and D is the number of days that the restructuring lasts (D ≤ 109 ).
Each of the next N lines describes a single machine for sale. Each line contains four integers Di , Pi , Ri and Gi ,
denoting (respectively) the day on which the machine is for sale, the dollar price for which it may be bought, the
dollar price for which it may be resold and the daily profit generated by operating the machine. These numbers satisfy
1 ≤ Di ≤ D, 1 ≤ Ri < Pi ≤ 109 and 1 ≤ Gi ≤ 109 .
The last test case is followed by a line containing three zeros.
Output
For each test case, display its case number followed by the largest number of dollars that ACM can have at the end of
day D + 1.
Follow the format of the sample output.
ICPC 2011 World Finals Problem F: Machine Works
Sample input Output for the Sample Input
6 10 20 Case 1: 44
6 12 1 3
1 9 1 2
3 2 1 2
8 20 5 4
4 11 7 4
2 10 9 1
0 0 0
ICPC 2011 World Finals Problem F: Machine Works
Editorial
Rendered from the copied solution.tex file. The original TeX source remains
available below.
Key Observations
Write the structural observations that make the problem tractable.
State any useful invariant, monotonicity property, graph interpretation, or combinatorial reformulation.
If the constraints matter, explain exactly which part of the solution they enable.
Algorithm
Describe the data structures and the state maintained by the algorithm.
Explain the processing order and why it is sufficient.
Mention corner cases explicitly if they affect the implementation.
Correctness Proof
We prove that the algorithm returns the correct answer.
Lemma 1.
State the first key claim.
Proof.
Provide a concise proof.
Lemma 2.
State the next claim if needed.
Proof.
Provide a concise proof.
Theorem.
The algorithm outputs the correct answer for every valid input.
Proof.
Combine the lemmas and finish the argument.
Complexity Analysis
State the running time and memory usage in terms of the input size.
Implementation Notes
Mention any non-obvious implementation detail that is easy to get wrong.
Mention numeric limits, indexing conventions, or tie-breaking rules if relevant.
Code
Exact copied C++ implementation from solution.cpp.
#include <bits/stdc++.h>
using namespace std;
namespace {
void solve() {
// Fill in the full solution logic for the problem here.
}
} // namespace
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
solve();
return 0;
}
Source Files
Exact copied source-of-truth files. Edit solution.tex for the write-up and solution.cpp for the implementation.
\documentclass[11pt]{article}
\usepackage[margin=1in]{geometry}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amssymb,amsthm}
\usepackage{enumitem}
\title{ICPC World Finals 2011\\F. Machine Works}
\author{}
\date{}
\begin{document}
\maketitle
\section*{Problem Summary}
State the problem in your own words. Focus on the mathematical or algorithmic core rather than repeating the full statement.
\section*{Key Observations}
\begin{itemize}[leftmargin=*]
\item Write the structural observations that make the problem tractable.
\item State any useful invariant, monotonicity property, graph interpretation, or combinatorial reformulation.
\item If the constraints matter, explain exactly which part of the solution they enable.
\end{itemize}
\section*{Algorithm}
\begin{enumerate}[leftmargin=*]
\item Describe the data structures and the state maintained by the algorithm.
\item Explain the processing order and why it is sufficient.
\item Mention corner cases explicitly if they affect the implementation.
\end{enumerate}
\section*{Correctness Proof}
We prove that the algorithm returns the correct answer.
\paragraph{Lemma 1.}
State the first key claim.
\paragraph{Proof.}
Provide a concise proof.
\paragraph{Lemma 2.}
State the next claim if needed.
\paragraph{Proof.}
Provide a concise proof.
\paragraph{Theorem.}
The algorithm outputs the correct answer for every valid input.
\paragraph{Proof.}
Combine the lemmas and finish the argument.
\section*{Complexity Analysis}
State the running time and memory usage in terms of the input size.
\section*{Implementation Notes}
\begin{itemize}[leftmargin=*]
\item Mention any non-obvious implementation detail that is easy to get wrong.
\item Mention numeric limits, indexing conventions, or tie-breaking rules if relevant.
\end{itemize}
\end{document}
#include <bits/stdc++.h>
using namespace std;
namespace {
void solve() {
// Fill in the full solution logic for the problem here.
}
} // namespace
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
solve();
return 0;
}