/*
Challenge Description:
Given a string S, and a list of strings of
positive length, F1,R1,F2,R2,...,FN,RN,
proceed to find in order the occurrences
(left-to-right) of Fi in S and replace them with Ri. All strings
are over alphabet { 0, 1 }.
Searching should consider only contiguous
pieces of S that have not been subject to replacements on prior iterations.
An iteration of the algorithm should not write
over any previous replacement by the algorithm.
Input sample:
Your program should accept as its first
argument a path to a filename.
Each line in this file is one test case. Each
test case will contain a string, then a semicolon and then a list of comma
separated strings.
E.g. 10011011001;0110,1001,1001,0,10,11
*/
import java.io.*;
class BadFileException extends Exception{
private static final long serialVersionUID = 1L;
public String
toString() {
return "Size of Fn not equal to size of Rn!";
}
}
public class Main {
public static void main(String
args[]){
if (args.length != 1) {
System.out.println("Error:
Bad command. Please enter filename.");
System.exit(0);
}
Main task = new Main();
task.stringModification(args[0]);
}
private String S;
public void
stringModification(String fileName) {
BufferedReader reader = null;
String strLine = "";
try {
reader = new
BufferedReader(new FileReader(fileName));
while ((strLine =
reader.readLine()) != null){
try {
replaceOneLine(strLine);
}
catch (BadFileException e) {
System.err.println(e.toString());
}
}
} catch
(FileNotFoundException e) {
System.err.println("Fail to find file");
} catch
(IOException e) {
System.err.println("Fail to read file");
}
}
private void
replaceOneLine(String str) throws BadFileException {
String line = str;
int pos =
line.indexOf(";");
S =
line.substring(0, pos);
line = line.replace(S+";", "");
String [] FnRn = line.split(",");
if (FnRn.length % 2 != 0) {
// Each Fi & Ri
comes in pair, so size of FnRn should be even.
throw new
BadFileException();
}
for (int i = 0; i
< FnRn.length; i += 2) {
replaceFiWithRi(FnRn[i],
FnRn[i+1]);
}
/* Re-convert 2 to 0 and 3 to 1. */
S = S.replaceAll("2", "0");
S = S.replaceAll("3", "1");
System.out.println(S);
}
private void
replaceFiWithRi(String Fi, String Ri) {
/* Temporarily convert 0 in Ri to 2, and 1 to 3,
so that later replacement will not write over any previous replacement.
*/
Ri = Ri.replaceAll("0", "2");
Ri = Ri.replaceAll("1", "3");
S = S.replace(Fi,
Ri);
}
}
