usaco-guide/content/1_Intro/Intro_Problems.md

slug	title	author	problems	order
/intro/problems	Introductory Problems	Nathan Wang, Benjamin Qi	bronze_promote bronze_word bronze_paint bronze_square	5

Demonstrates how to read in input and print output for a USACO problem in multiple languages. Also lists some introductory USACO Bronze problems.

Technical Specifications for Contests

Example: Fence Painting

USACO will automatically add a newline to the end of your file if it does not end with one. Make sure not to output trailing spaces!

C++

You can use ios_base::sync_with_stdio(0); cin.tie(0); to speed up input and output. See here and StackOverflow for more information. Apparently if this is included then it is supposedly prohibited to use freopen to redirect cin and cout, but it works properly on USACO (and I believe that it does in fact result in a significant speedup on large input files).

Method 1

Use freopen. If you comment out both of the lines containing freopen then the program reads from standard in and writes to standard out as usual.

#include <bits/stdc++.h>
using namespace std;

int main() {
	freopen("paint.in","r",stdin); // reuse standard in to read from "paint.in"
	freopen("paint.out","w",stdout); // reuse standard out to write to "paint.out"
	vector<bool> cover(100);
	int a, b, c, d; cin >> a >> b >> c >> d;
	for (int i = a; i < b; ++i) cover[i] = 1;
	for (int i = c; i < d; ++i) cover[i] = 1;
	int ans = 0; 
	for (int i = 0; i < 100; ++i) ans += cover[i];
	cout << ans; 
	// cout << ans << "\n"; is OK
	// cout << ans << " "; is NOT
	// cout << ans << "\n\n"; is NOT
}

Method 2

Use ifstream & ofstream.

#include <bits/stdc++.h>
using namespace std;

int main() {
	ifstream fin("paint.in");
	ofstream fout("paint.out");
	vector<bool> cover(100);
	int a, b, c, d; fin >> a >> b >> c >> d;
	for (int i = a; i < b; ++i) cover[i] = 1;
	for (int i = c; i < d; ++i) cover[i] = 1;
	int ans = 0; 
	for (int i = 0; i < 100; ++i) ans += cover[i];
	fout << ans;
}

Java

(link?)

(Scanner?)

(FastScanner?)

Class name can be whatever you want. (?)

import java.io.*;
import java.util.*;
public class paintSol { // must be declared in paintSol.java
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new FileReader("paint.in"));
		PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("paint.out")));
		int[] cover = new int[100];

		StringTokenizer st = new StringTokenizer(br.readLine());
		int a = Integer.parseInt(st.nextToken()), b = Integer.parseInt(st.nextToken());
		st = new StringTokenizer(br.readLine());
		int c = Integer.parseInt(st.nextToken()), d = Integer.parseInt(st.nextToken());

		for (int i = a; i < b; ++i) cover[i] = 1;
		for (int i = c; i < d; ++i) cover[i] = 1;
		int ans = 0; 
		for (int i = 0; i < 100; ++i) ans += cover[i];
		pw.println(ans); 
		pw.close(); // make sure to include this line ...
	}
}

Python 3

See here.

fin = open("paint.in","r")
fout = open("paint.out","w")
cover = [0 for i in range(100)]
a,b = map(int,fin.readline().split())
c,d = map(int,fin.readline().split())
for i in range(a,b):
	cover[i] = 1
for i in range(c,d):
	cover[i] = 1
ans = 0
for i in range(100):
	ans += cover[i]
fout.write(str(ans))

Problems

Let's begin by solving a few problems! The following require relatively little programming experience and no algorithmic knowledge.

Do as many as you want, then move on! You do not have to do all of them.

• Promotion Counting
• Word Processor
• Square Pasture