teaching machines

CS 145 Lecture 16 – Arrays

November 4, 2011 by Chris Johnson. Filed under cs145, fall 2011, lectures.

Agenda

• named data vs. numbered data
• arrays
• mapping month numbers to names
• the birthday problem

Code

Birthdays

9 6
3 30
9 26
10 11
7 6
12 7
1 9
2 10
6 21
3 2
5 12
2 25
7 3
1 17
4 29
5 19
12 8
4 2
3 31
5 30
11 30
5 30
3 8
9 15
9 5
10 24
6 5
8 8
6 14
4 29
11 15
4 7
2 14
6 29
4 7
2 16
8 31
6 29
8 21
4 18
2 10
7 18
2 16
9 15
8 10
12 21
10 24
12 9
3 23
4 1
6 25
4 14
2 14
1 10
2 14
10 24
3 15
4 16
9 11
10 14
10 19
10 1
9 28
1 10
9 28
8 30
4 25
6 21
5 21
6 14
8 14
11 11
5 17
1 20
11 6
10 7
4 20
12 27
4 9
12 3
11 29
1 20
10 26
10 26
3 27
8 9
11 18
5 1
7 29
3 3
6 14
3 29
5 10

Birthdayarator.java

package lecture;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class Birthdayarator {
  public static void main(String[] args) throws FileNotFoundException {
    Scanner in = new Scanner(new File("/home/cjohnson/Desktop/bdays.txt"));
    
    String[] names = new String[12];
    names[0] = "January";
    names[1] = "February";
    names[2] = "March";
    names[3] = "April";
    names[4] = "May";
    names[5] = "June";
    names[6] = "July";
    names[7] = "August";
    names[8] = "September";
    names[9] = "October";
    names[10] = "November";
    names[11] = "December";
    
    int[] counts = new int[12 * 31];
    
    System.out.println(names.length);
    
    while (in.hasNextInt()) {
      int month = in.nextInt();
      int day = in.nextInt();
      
      int doy = (month - 1) * 31 + day;
      ++counts[doy];
      
      String monthName = names[month - 1];
      System.out.print(monthName);
      
//      if (month == 1) {
//        System.out.print("January");
//      } else if (month == 2) {
//        System.out.print("February");
//      } else if (month == 3) {
//        System.out.print("March");
//      } else if (month == 4) {
//        System.out.print("April");
//      } else if (month == 5) {
//        System.out.print("May");
//      } else if (month == 6) {
//        System.out.print("June");
//      } else if (month == 7) {
//        System.out.print("July");
//      } else if (month == 8) {
//        System.out.print("August");
//      } else if (month == 9) {
//        System.out.print("September");
//      } else if (month == 10) {
//        System.out.print("October");
//      } else if (month == 11) {
//        System.out.print("November");
//      } else if (month == 12) {
//        System.out.print("December");
//      } else {
//        System.out.println("YOUR PROGRAM IS BJORKED");
//      }
      System.out.println(" " + day);
    }
    
    for (int i = 0; i < counts.length; ++i) {
      if (counts[i] > 1) {
        System.out.println(i);
      }
    }
  }
}

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