Question

Overview:

Pattern-Matching (aka String Search) is the process of algorithmically finding copies of a pattern P inside a (generally much larger) text T. The goal is to implement and compare four classical string-matching algorithms.

Input:

Your code should work for any text either inputted directly or read in from a file.

However, for testing - input file has been provided:

• The Gettysburg Address (by President Abraham Lincoln, 1863)

You should minimally search for these three patterns in each text: FREE, BRAVE, NATION.

You should convert the entire string to upper case and conduct your searches accordingly.

Methodology and Output:

1. Implement the Brute Force Algorithm

2. Implement the Knuth-Morris-Pratt Algorithm

3. For each algorithm and text/pattern combination

   a)Track and tabulate the number of character-comparison operations   b)Track and tabulate the clock time for each algorithm

Input file for test:

The Gettysburg Address.txt

Fourscore and seven years ago our fathers brought forth on this continent a new nation, conceived in liberty and dedicated to the proposition that all men are created equal. Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure. We are met on a great battlefield of that war. We have come to dedicate a portion of that field as a final resting-place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this. But, in a larger sense, we cannot dedicate — we cannot consecrate — we cannot hallow — this ground. The brave men, living and dead, who struggled here have consecrated it, far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us — that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion — that we here highly resolve that these dead shall not have died in vain — that this nation shall have a new birth of freedom and that government of the people, by the people, for the people, shall not perish from the earth.

Code in JAVA thanks

Answer 1

Working code implemented in Java and appropriate comments provided for better understanding:

Here I am attaching code for these files:

• StringSearch.java
• Print.java
• KMP.java

Source code for StringSearch.java:

import java.util.*;
import java.io.*;

public class StringSearch{
static Map<Integer, String> inputTextMap;
static Map<Integer, String> searchTextMap;
static String inputText = "", searchText = "";
static long time = 0;
static int comp=0, searchIndex=1, textIndex =1;
public static void main(String[] args)throws FileNotFoundException{
System.out.print("===============\n");
System.out.print("BruteForce\n");
System.out.print("===============");
inputTextMap = new HashMap();
searchTextMap = new HashMap();
textIndex = 1;
searchIndex = 1;
inputTextMap.put(1, "Gettysburg Address");
inputTextMap.put(2, "Star Spangled Banner");
inputText = inputTextMap.get(searchIndex);

String s = readFile(textIndex);

searchTextMap.put(1,"FREE");
searchTextMap.put(2,"BRAVE");
searchTextMap.put(3,"NATION");
for(int i=1; i<=3; i++){
searchText = searchTextMap.get(searchIndex);
bruteForce(s, searchTextMap.get(searchIndex++));
}
  
}
public static String readFile(int n)throws FileNotFoundException{
String read = "input"+Integer.toString(n)+".txt";
File file = new File(read);
Scanner sc = new Scanner(file);
StringBuilder sb = new StringBuilder();

while(sc.hasNext()){
sb.append(sc.nextLine());
}
return sb.toString().toUpperCase();
}

public static void bruteForce(String text, String find){
long start = System.currentTimeMillis();
time = start;
for(int i=0; i<=text.length()-find.length(); i++){
int j;
for(j=0; j<find.length(); j++){
comp++;
if(text.charAt(i+j) != find.charAt(j)){
break;
}
}
  
if(j == find.length()){
long end = System.currentTimeMillis();
time = end-time;
Print p = new Print(i,comp,time,searchText,inputText);
p.print(p);
return;
}
}
}
}

Source code for Print.java:

public class Print {
int index, compare;
long time;
String text, search;

public Print(){
this.index = 0;
this.compare = 0;
this.time = 0;
this.text = "";
this.search = "";
}

public Print(int index, int compare, long time, String text, String search){
this.index = index;
this.compare = compare;
this.time = time;
this.text = text;
this.search = search;
}
public static void print(Print p) {
System.out.println();
System.out.printf("%15s %25s %25s %25s %25s %1s", "First Index", "Comparisons", "Time","Input Text","Search word", "\n");
System.out.printf("%15d %22d %25dms %25s %25s", p.index, p.compare, p.time, p.text, p.search);
System.out.println();
}
}

Source code for KMP.java:

import java.util.*;
import java.io.*;

public class KMP {
static Map<Integer, String> inputTextMap;
static Map<Integer, String> searchTextMap;
static String inputText = "", searchText = "";
static long time = 0;
static int comp=0, searchIndex=1, textIndex =1;
public static void main(String[] args)throws FileNotFoundException{
System.out.print("===============\n");
System.out.print("KMP\n");
System.out.print("===============");
inputTextMap = new HashMap();
searchTextMap = new HashMap();
textIndex = 1;
searchIndex = 1;
inputTextMap.put(1, "Gettysburg Address");
inputTextMap.put(2, "Star Spangled Banner");
inputText = inputTextMap.get(textIndex);

String s = readFile(textIndex);

searchTextMap.put(1,"FREE");
searchTextMap.put(2,"BRAVE");
searchTextMap.put(3,"NATION");
for(int i=1; i<=3; i++){
searchText = searchTextMap.get(searchIndex);
kmp(s, searchTextMap.get(searchIndex++));
}
  
}
public static String readFile(int n)throws FileNotFoundException{
String read = "input"+Integer.toString(n)+".txt";
File file = new File(read);
Scanner sc = new Scanner(file);
StringBuilder sb = new StringBuilder();

while(sc.hasNext()){
sb.append(sc.nextLine());
}
return sb.toString().toUpperCase();
}

public static void kmp(String search, String pattern){
long start = System.currentTimeMillis();
time = start;
int[] lpsarr = new int[pattern.length()];
int j = 0;

lps(pattern, pattern.length(), lpsarr);
int i = 0;
while(i < search.length()){
comp++;
if(pattern.charAt(j) == search.charAt(i)){
i++;
j++;
}
if(j == pattern.length()){
long end = System.currentTimeMillis();
time = end-start;
Print p = new Print(i,comp,time,searchText,inputText);
p.print(p);
return;
}
else if(i < search.length() && pattern.charAt(j) != search.charAt(i)){
if(j != 0){
comp++;
j = lpsarr[j-1];
}else{
i++;
}
}
}

}

public static void lps(String s, int length, int[] lpsarr){
int len = 0;
int i=1;
lpsarr[0] = 0;

while(i < length){
if(s.charAt(i) == s.charAt(len)){
len++;
lpsarr[i++] = len;
}else{
if(len != 0){
len = lpsarr[len-1];
}else{
lpsarr[i++] = len;
}
}
}
}
}

Sample Output Screenshots:

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