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Problem solution · Java

CCC 2013 S1 - From 1987 to 2013

CCC 2013 S1 - From 1987 to 2013: a Java solution using sorting and greedy selection. Learn the idea, check the complexity, and read the full code, with credit to CCCSolutions.

Technique
Sorting and greedy selection
Source
CCCSolutions
Length
37 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

Sorting and greedy selection

For CCC 2013 S1 - From 1987 to 2013, the implementation first exposes a useful order, then scans that order while making locally justified choices.

  1. Choose the key that reveals the greedy or grouping structure.
  2. Sort the relevant records by that key.
  3. Scan in order, maintaining the invariant that makes each local choice safe.

Code notes

  • 37 lines of Java from the credited upstream file ccc13s1.java.
  • The implementation visibly relies on sequence storage.
  • 2 loop blocks detected.

Complexity

Sorting is typically the dominant term unless the subsequent scan uses a more expensive nested operation.

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 2013 S1 - From 1987 to 2013 · JavaJava
Use this to learn the idea, then write your own version.
//Ivan Li, Markville secondary schoolimport java.io.*;import java.util.*; public class Main {    public static void main(String[] args) {        Scanner sc = new Scanner(System.in);        int year = sc.nextInt()+1;        while(true){                       char A[] = Integer.toString(year).toCharArray();            boolean distinct = false;            Arrays.sort(A);            for(int i=0; i<A.length-1; i++){                if(A[i]==A[i+1]){                     distinct = true;                }            }            if(distinct==false){                System.out.println(year);                return;            }            else{                year++;            }        }                             }}

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