Skip to content

Commit add6448

Browse files
HarryDulaneyHarryDulaney
committed
Chap 21, Ex: 14,15.
1 parent 20da60e commit add6448

File tree

4 files changed

+146
-12
lines changed

4 files changed

+146
-12
lines changed

‎ch_07/Exercise07_02.java

+1
Original file line numberDiff line numberDiff line change
@@ -13,6 +13,7 @@ public static void main(String[] args) {
1313

1414
Scanner input = new Scanner(System.in);
1515
System.out.println("Enter ten space-separated integers: ");
16+
1617
int[] arr = new int[10];
1718

1819
for (int i = 0; i < 10; i++) {

‎ch_08/Exercise08_36.java

+3-12
Original file line numberDiff line numberDiff line change
@@ -39,7 +39,6 @@ public static void main(String[] args) {
3939
char[][] chars = new char[numRows][numRows];
4040

4141
int upperBoundChar = minChar + numRows - 1; //Upper Bound for the range from 'A' -> ('A' + userInput)
42-
4342
System.out.println("\nEnter " + numRows + " rows of capital letters separated by spaces: ");
4443
try {
4544
for (int r = 0; r < chars.length; r++) {
@@ -54,7 +53,7 @@ public static void main(String[] args) {
5453
} catch (Exception e) {
5554
e.printStackTrace();
5655
System.out.println(e.getLocalizedMessage());
57-
notALSq();
56+
System.out.println("The input array is not a Latin Square.");
5857
System.exit(0);
5958
}
6059

@@ -78,7 +77,7 @@ public static void main(String[] args) {
7877

7978
} else if (rowTracker.size() != 0) {
8079
if (rowTracker.contains(charValue)) {
81-
notALSq();
80+
System.out.println("The input array is not a Latin Square.");
8281
result = false;
8382
break ROW;
8483
}
@@ -99,7 +98,7 @@ public static void main(String[] args) {
9998

10099
if (colTracker.size() > 0) {
101100
if (colTracker.contains(value)) {
102-
notALSq();
101+
System.out.println("The input array is not a Latin Square.");
103102
break OUTER;
104103
}
105104
}
@@ -109,12 +108,4 @@ public static void main(String[] args) {
109108
}
110109
in.close();
111110
}
112-
113-
static void notALSq() {
114-
System.out.println("The input array is not a Latin Square.");
115-
}
116-
117-
static void aLsq() {
118-
System.out.println("The input array is a Latin Square.");
119-
}
120111
}

‎ch_21/Exercise21_14.java

+99
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,99 @@
1+
package ch_21;
2+
3+
import java.net.URL;
4+
import java.util.*;
5+
6+
/**
7+
* *21.14 (Web crawler) Rewrite Listing 12.18, WebCrawler.java,
8+
* to improve the performance by using appropriate
9+
* new data structures for listOfPendingURLs and listofTraversedURLs.
10+
*/
11+
public class Exercise21_14 {
12+
public static void main(String[] args) {
13+
java.util.Scanner input = new java.util.Scanner(System.in);
14+
System.out.print("Enter a URL: ");
15+
String url = input.nextLine();
16+
crawler(url); // Traverse the Web from the a starting url
17+
}
18+
19+
public static void crawler(String startingURL) {
20+
/* Exercise 21.14
21+
...improve the performance by using appropriate new data structures for listOfPendingURLs and
22+
listofTraversedURLs.
23+
*/
24+
TreeSet<CrawlUrl> listOfPendingURLs = new TreeSet<>();
25+
HashSet<CrawlUrl> listOfTraversedURLs = new HashSet<>();
26+
listOfPendingURLs.add(new CrawlUrl(startingURL));
27+
while (!listOfPendingURLs.isEmpty() &&
28+
listOfTraversedURLs.size() <= 100) {
29+
CrawlUrl crawUrl = listOfPendingURLs.first();
30+
listOfPendingURLs.remove(crawUrl);
31+
if (!listOfTraversedURLs.contains(crawUrl)) {
32+
listOfTraversedURLs.add(crawUrl);
33+
System.out.println("Crawl: " + crawUrl);
34+
for (CrawlUrl crawlUrl : getSubURLs(crawUrl.getUrlString())) {
35+
if (!listOfTraversedURLs.contains(crawlUrl))
36+
listOfPendingURLs.add(crawlUrl);
37+
}
38+
}
39+
}
40+
}
41+
42+
public static Set<CrawlUrl> getSubURLs(String urlString) {
43+
Set<CrawlUrl> set = new HashSet<>(); // Exercise 21.14
44+
try {
45+
URL url = new URL(urlString);
46+
Scanner input = new Scanner(url.openStream());
47+
int current = 0;
48+
while (input.hasNext()) {
49+
String line = input.nextLine();
50+
current = line.indexOf("http:", current);
51+
while (current > 0) {
52+
int endIndex = line.indexOf("\"", current);
53+
if (endIndex > 0) { // Ensure that a correct URL is found
54+
set.add(new CrawlUrl(line.substring(current, endIndex)));
55+
current = line.indexOf("http:", endIndex);
56+
} else
57+
current = -1;
58+
}
59+
}
60+
} catch (Exception ex) {
61+
System.out.println("Error: " + ex.getMessage());
62+
}
63+
return set;
64+
}
65+
}
66+
67+
/**
68+
* Implements Comparable for default sorting when used in a TreeSet
69+
*/
70+
class CrawlUrl implements Comparable<CrawlUrl> {
71+
private String urlString;
72+
73+
public CrawlUrl(String urlString) {
74+
this.urlString = urlString;
75+
}
76+
77+
@Override
78+
public int compareTo(CrawlUrl that) {
79+
// Implement to sort by the length of the url
80+
return Integer.compare(this.urlString.length(), that.urlString.length());
81+
}
82+
83+
public String getUrlString() {
84+
return urlString;
85+
}
86+
87+
public CrawlUrl setUrlString(String urlString) {
88+
this.urlString = urlString;
89+
return this;
90+
}
91+
92+
93+
@Override
94+
public String toString() {
95+
return "CrawlUrl{" +
96+
"urlString='" + urlString + '\'' +
97+
'}';
98+
}
99+
}

‎ch_21/Exercise21_15.java

+43
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,43 @@
1+
package ch_21;
2+
3+
import java.util.HashSet;
4+
import java.util.Scanner;
5+
import java.util.Set;
6+
7+
/**
8+
* *21.15 (Addition quiz) Rewrite Programming Exercise 11.16 to store the answers in a
9+
* set rather than a list.
10+
* <p>
11+
* {@linkplain ch_11.Exercise11_16}
12+
*/
13+
public class Exercise21_15 {
14+
public static void main(String[] args) {
15+
Set<Integer> guesses = new HashSet<>();
16+
17+
Scanner input = new Scanner(System.in);
18+
19+
int number1 = (int) (Math.random() * 10);
20+
int number2 = (int) (Math.random() * 10);
21+
22+
System.out.print("What is " + number1 + " + " + number2 + "? ");
23+
int answer = input.nextInt();
24+
25+
while (answer != number1 + number2) {
26+
27+
if (guesses.contains(answer)) {
28+
System.out.println("You've already entered " + answer);
29+
System.out.print("Try again. What is " + number1 + " + " + number2 + "? ");
30+
answer = input.nextInt();
31+
32+
} else {
33+
guesses.add(answer);
34+
System.out.print("Wrong answer. Try again. What is " + number1 + " + " + number2 + "? ");
35+
answer = input.nextInt();
36+
}
37+
38+
}
39+
40+
input.close();
41+
System.out.println("You got it!");
42+
}
43+
}

0 commit comments

Comments
 (0)