java/03-arrays/Students Source

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Property Value

Description
html markup
shown to student

Read an integer N from standard input, then a list
of N student records, where each record consists of four
fields, separated by whitespace:
<ul>
<li>first name</li>
<li>last name</li>
<li>email address</li>
<li>which section they're in</li>
</ul>
Then, print a list of email address of students in sections 4 and 5.
(Booksite Web Exercise 1.5.31)

<div>
For example, if the standard input is
<pre>
6
Bob Sedgewick rs 1
Kevin Wayne wayne 4
Donna Gabai dgabai 5
David Pritchard dp6 6
Judith Israel jlisrael 3
Alan Turing turing 4
</pre>
Then the output should be
<pre>
Section 4
---------
wayne
turing

Section 5
---------
dgabai
</pre>

Epilogue
html markup
shown when solved

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Remarks
Comments, history, license, etc.

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Engine
Choices
json list of string, bool pairs
e.g. [["good", true], ["bad", false]]

Correct answer
Template / Reference solution

public static void main(String[] args) {

// read the number of students
int N = \[StdIn.readInt()]\ ;

// declare and initialize four parallel arrays
String[] first = new String[N];
\[String[]]\ last = \[new String[N]]\;
String[] \[email]\ = \[new String[N]]\;
int[] section = \[new int[N]]\;

// read in the data from standard input
for (\[int i=0; i<N; i++]\) {
first[\[i]\] = \[StdIn.readString();]\
last[\[i]\] = \[StdIn.readString();]\
email[\[i]\] = \[StdIn.readString();]\
section[\[i]\] = \[StdIn.readInt();]\
}

// print email addresses of all students in section 4
StdOut.println("Section 4");
StdOut.println("---------");
for (int i = 0; i < N; i++) {
if (\[section[i] == 4]\) {
StdOut.println(\[email[i]]\);
}
}
StdOut.println(); // blank line

// print email addresses of all students in section 5
StdOut.println("Section 5");
StdOut.println("---------");
for \[(int i = 0; i < N; i++)]\ {
\[
if (section[i] == 5) {
StdOut.println(email[i]);
}
]\
}
}

Template / Reference solution

Java test suite
See manual

stdin = "6\nBob Sedgewick rs 1\nKevin Wayne wayne 4\nDonna Gabai dgabai 5\nDavid Pritchard dp6 6\nJudith Israel jlisrael 3\nAlan Turing turing 4";
testMain();
stdinURL = "http://introcs.cs.princeton.edu/java/15inout/students.txt";
testMain();
stdin = "1\nJoe Student joestu 0\nYour program should only have read 1 student for this input";
testMain();

C++ test suite
json list of stdin/args tests
e.g. [{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]
to just run once with no input use [{}]

C++ test suite
See manual

Forbidden substrings
json list of strings
e.g. ["for","while"]

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Solution visibility remove
Java imports
json list of importables
e.g. ["java.util.*"]

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Override Java classname
else defaults to
websheet name
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Dependent on other websheets?
json list of websheet names in this folder
e.g. ["DataStructure"]

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Is example?
i.e., just a demo
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Add compiler flag(s)
json list of flags
e.g. ["-Wno-unused-variable"]

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Remove default compiler flag(s)
json list of flags
see default_cppflags
e.g. ["-Wno-write-strings"]

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Property	Value
Description html markup shown to student	Read an integer N from standard input, then a list of N student records, where each record consists of four fields, separated by whitespace: <ul> <li>first name</li> <li>last name</li> <li>email address</li> <li>which section they're in</li> </ul> Then, print a list of email address of students in sections 4 and 5. (Booksite Web Exercise 1.5.31) <div> For example, if the standard input is <pre> 6 Bob Sedgewick rs 1 Kevin Wayne wayne 4 Donna Gabai dgabai 5 David Pritchard dp6 6 Judith Israel jlisrael 3 Alan Turing turing 4 </pre> Then the output should be <pre> Section 4 --------- wayne turing Section 5 --------- dgabai </pre>
Epilogue html markup shown when solved	remove
Public permissions	remove
Remarks Comments, history, license, etc.	remove
Engine
Choices json list of string, bool pairs e.g. `[["good", true], ["bad", false]]`
Correct answer
Template / Reference solution	public static void main(String[] args) { // read the number of students int N = \[StdIn.readInt()]\ ; // declare and initialize four parallel arrays String[] first = new String[N]; \[String[]]\ last = \[new String[N]]\; String[] \[email]\ = \[new String[N]]\; int[] section = \[new int[N]]\; // read in the data from standard input for (\[int i=0; i<N; i++]\) { first[\[i]\] = \[StdIn.readString();]\ last[\[i]\] = \[StdIn.readString();]\ email[\[i]\] = \[StdIn.readString();]\ section[\[i]\] = \[StdIn.readInt();]\ } // print email addresses of all students in section 4 StdOut.println("Section 4"); StdOut.println("---------"); for (int i = 0; i < N; i++) { if (\[section[i] == 4]\) { StdOut.println(\[email[i]]\); } } StdOut.println(); // blank line // print email addresses of all students in section 5 StdOut.println("Section 5"); StdOut.println("---------"); for \[(int i = 0; i < N; i++)]\ { \[ if (section[i] == 5) { StdOut.println(email[i]); } ]\ } }
Template / Reference solution
Java test suite See manual	stdin = "6\nBob Sedgewick rs 1\nKevin Wayne wayne 4\nDonna Gabai dgabai 5\nDavid Pritchard dp6 6\nJudith Israel jlisrael 3\nAlan Turing turing 4"; testMain(); stdinURL = "http://introcs.cs.princeton.edu/java/15inout/students.txt"; testMain(); stdin = "1\nJoe Student joestu 0\nYour program should only have read 1 student for this input"; testMain();
C++ test suite json list of stdin/args tests e.g. `[{"stdin":"hi", "args":["4", "5"]}, {"stdin":"noargs"}]` to just run once with no input use `[{}]`
C++ test suite See manual
Forbidden substrings json list of strings e.g. `["for","while"]`	remove
Solution visibility	remove
Java imports json list of importables e.g. `["java.util.*"]`	remove
Override Java classname else defaults to websheet name	remove
Dependent on other websheets? json list of websheet names in this folder e.g. `["DataStructure"]`	remove
Is example? i.e., just a demo	remove
Add compiler flag(s) json list of flags e.g. `["-Wno-unused-variable"]`	remove
Remove default compiler flag(s) json list of flags see default_cppflags e.g. `["-Wno-write-strings"]`	remove

Optional properties:

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