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Problem solution · Java

CCC 2008 S1 - It's Cold Here

CCC 2008 S1 - It's Cold Here: a Java solution using binary search. Learn the idea, check the complexity, and read the full code, with credit to CCCSolutions.

Technique
Binary search
Source
CCCSolutions
Length
39 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Binary search

For CCC 2008 S1 - It's Cold Here, the implementation exploits a monotonic condition to discard half of the remaining search space after every check.

  1. Identify the ordered answer range or sorted search domain.
  2. Write a predicate whose truth changes only once.
  3. Move the appropriate boundary after each midpoint check and return the final feasible position.

Code notes

  • 39 lines of Java from the credited upstream file ccc08s1.java.
  • The implementation visibly relies on sequence storage.
  • 1 loop block detected.

Complexity

Multiply the logarithmic number of midpoint checks by the cost of one predicate evaluation.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from CCCSolutions by CCCSolutions contributors · Milliken Mills High School and is used under the MIT licence.

Open problem ↗Original source ↗
Full codeCCC 2008 S1 - It's Cold Here · JavaJava
Use this to learn the idea, then write your own version.
// CCC 2008//// S1: It's Cold Here//// this is the classic "find smallest" number problem// (The trick is to set the 1st one to the smallest, or coldest)// import java.awt.*;import hsa.*; public class CCC2008S1ItsColdHere{    static Console c;     public static void main (String[] args)    {	String city, coldestCity;	int temp, coldest;	c = new Console ();	TextInputFile f = new TextInputFile ("s1.3.in"); 	city = f.readString ();	coldestCity = city;	coldest = f.readInt ();	while (!city.equals ("Waterloo"))	{	    city = f.readString ();	    temp = f.readInt ();	    if (temp < coldest)	    {		coldestCity = city;		coldest = temp;	    }	}	c.println (coldestCity);    }}

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