Develop Reference

Finding the longest substring between a "start" string and one of 3 possible "end" strings

So my question is substring-related.
How do you find the longest possible substring between a starting string and one of three ending strings? I also need to find the index of the original string that the largest substring starts at.
So:
Start string:
"ATG"
3 possible end strings:
"TAG"
"TAA"
"TGA"
An example original string might be:
"SDAFKJDAFKATGDFSDFAKJDNKSJFNSDTGASDFKJSDNKFJSNDJFATGDSDFKJNSDFTAGSDFSDATGFF"
So the result of that should give me:
- Longest substring length: 23 (from the substring ATGDFSDFAKJDNKSJFNSDTGA)
- Index of longest substring: 10
I cannot use Regex.
Thanks for any help!

This is arguably the easiest way, and it's just one line:
String target = str.replaceAll(".*ATG(.*)(TAG|TAA|TGA).*", "$1");
To find the index:
int index = str.indexOf("ATG") + 3;
Note: I have interpreted your remark "I cannot use regex" to mean "I am unskilled at regex", because if it's a java question, regex is available.

Well, this looks like a fun one.
It seems the most straightforward way to do this would be to build your own mini finite state machine. You would have to parse each character in the string and keep track of all possible character sequences that would terminate the sequence.
If you hit a 'T', you need to jump ahead and look at the next character. If it's an 'A' or a 'G' you need to jump ahead again, otherwise, add those tokens to your string. Continue the pattern until you get to the end of the original string, or match one of your terminal patterns.
So, maybe something that looks like this (simplified example):
String longestSequence(String original) {
StringBuilder sb = new StringBuilder();
char[] tokens = original.toCharArray();
for (int i = 0; i < tokens.length; ++i) {
// read each token, and compare / look ahead to see if you should keep going or terminate.
}
return sb.toString();
}

match your string to this regex:
ATG[A-Z]+(TAG|TAA|TGA)
if multiple match occurs then iterate and keep the one with highest length.
import java.util.regex.Matcher;
import java.util.regex.Pattern;
// using pattern with flags
Pattern pattern = Pattern.compile("ATG[A-Z]+(TAG|TAA|TGA)");
Matcher matcher = pattern.matcher( yourInputStringHere );
while (matcher.find()) {
System.out.println("Found the text \"" + matcher.group()
+ "\" starting at " + matcher.start()
+ " and ending at index " + matcher.end());
}

There are already some beautiful and elegant solutions to your problem (Bohemian and inquisitive). If you still - as originally stated - can't use regex, here's an alternative. This code is not especially elegant, and as pointed, there are better ways to do it, but it should at least clearly show you the logic behind the solution to your problem.
How do you find the longest possible substring between a starting string
and one of three ending strings?
First, find the index of starting string, then find the index of each ending string, and get substrings for each ending, then their length. Remember that if string is not found, its index will be -1.
String originalString = "SDAFKJDAFKATGDFSDFAKJDNKSJFNSDTGASDFKJSDNKFJSNDJFATGDSDFKJNSDFTAGSDFSDATGFF";
String STARTING_STRING = "ATG";
String END1 = "TAG";
String END2 = "TAA";
String END3 = "TGA";
//let's find the index of STARTING_STRING
int posOfStartingString = originalString.indexOf(STARTING_STRING);
//if found
if (posOfStartingString != -1) {
int tagPos[] = new int[3];
//let's find the index of each ending strings in the original string
tagPos[0] = originalString.indexOf(END1, posOfStartingString+3);
tagPos[1] = originalString.indexOf(END2, posOfStartingString+3);
tagPos[2] = originalString.indexOf(END3, posOfStartingString+3);
int lengths[] = new int[3];
//we can now use the following methods:
//public String substring(int beginIndex, int endIndex)
//where beginIndex is our posOfStartingString
//and endIndex is position of each ending string (if found)
//
//and finally, String.length() to get the length of each substring
if (tagPos[0] != -1) {
lengths[0] = originalString.substring(posOfStartingString, tagPos[0]).length();
}
if (tagPos[1] != -1) {
lengths[1] = originalString.substring(posOfStartingString, tagPos[1]).length();
}
if (tagPos[2] != -1) {
lengths[2] = originalString.substring(posOfStartingString, tagPos[2]).length();
}
} else {
//no starting string in original string
}
lengths[] table now contains length of strings starting with STARTING_STRING and 3 respective endings. Then just find which one is the longest and you will have your answer.
I also need to find the index of the original string that the largest substring starts at.
This will be the index of where starting string starts, in this case 10.

why does this for loop wordcount method not work in java

Can anyone let me know why this wordsearch method doesn't work - the returned value of count is 0 everytime I run it.
public int wordcount(){
String spaceString = " ";
int count = 0;
for(int i = 0; i < this.getString().length(); i++){
if (this.getString().substring(i).equals(spaceString)){
count++;
}
}
return count;
}
The value of getString = my search string.
Much appreciated if anyone can help - I'm sure I'm prob doing something dumb.
Dylan

Read the docs:
The substring begins with the character at the specified index and extends to the end of this string.
Your if condition is only true once, if the last character of the string is a space. Perhaps you wanted charAt? (And even this won't properly handle double spaces; splitting on whitespace might be a better option.)

Because substring with only one argument returns the sub string starting from that index till the end of the string. So you're not comparing just one character.
Instead of substring define spaceString as a char, and use charAt(i)

this.getString().substring(i) -> this returns a sub string from the index i to the end of the String
So for example if your string was Test the above would return Test, est, st and finally t
For what you're trying to do there are alternative methods, but you could simple replace
this.getString().substring(i)
with
spaceString.equals(this.getString().charAt(i))
An alternative way of doing what you're trying to do is:
this.getString().split(spaceString)
This would return an array of Strings - the original string broken up by spaces.

Read the documentation of the method you are using:
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#substring(int)
I.e. the count will be non zero only if you have a space on the end of your string

Using substring as you are will not work. If the value of getString() is "my search string" every iteration through the loop with have substring(i) return:
my search string
y search string
search string
search string
earch string
arch string
rch string
ch string
h string
string
string
tring
ring
ing
ng
g
Notice none of those equals " ".
Try using split.
public int countWords(String s){
return s.split("\\s+").length;
}

Change
if (this.getString().substring(i).equals(spaceString))
to
if (this.getString().charAt(i) == ' ')

this.getString().substring(i) returns a string from the index of (i) to the end of the string.
Example: for i=5, it will return "rown cow" from the string "the brown cow". This functionality isn't what you need.
If you pepper System.out.println() throughout your code (or use the debugger), you will see this.
I think it would be better to use something like String.split() or charAt(i).
By the way, even if you fix your code by counting spaces, it will not return the correct value for these conditions: "my dog" (word count=2) and "cow" (word count=1). There is also a problem if there are more than one space between words. ALso, this will produce a word cound of three:
" the cow ".

Is it possible to get only the first character of a String?

I have a for loop in Java.
for (Legform ld : data)
{
System.out.println(ld.getSymbol());
}
The output of the above for loop is
Pad
CaD
CaD
CaD
Now my question is it possible to get only the first characer of the string instead of the whole thing Pad or CaD
For example if it's Pad I need only the first letter, that is P
For example if it's CaD I need only the first letter, that is C
Is this possible?

Use ld.charAt(0). It will return the first char of the String.
With ld.substring(0, 1), you can get the first character as String.

String has a charAt method that returns the character at the specified position. Like arrays and Lists, String is 0-indexed, i.e. the first character is at index 0 and the last character is at index length() - 1.
So, assuming getSymbol() returns a String, to print the first character, you could do:
System.out.println(ld.getSymbol().charAt(0)); // char at index 0

The string has a substring method that returns the string at the specified position.
String name="123456789";
System.out.println(name.substring(0,1));

Here I am taking Mobile No From EditText It may start from +91 or 0 but i am getting actual 10 digits.
Hope this will help you.
String mob=edit_mobile.getText().toString();
if (mob.length() >= 10) {
if (mob.contains("+91")) {
mob= mob.substring(3, 13);
}
if (mob.substring(0, 1).contains("0")) {
mob= mob.substring(1, 11);
}
if (mob.contains("+")) {
mob= mob.replace("+", "");
}
mob= mob.substring(0, 10);
Log.i("mob", mob);
}

Answering for C++ 14,
Yes, you can get the first character of a string simply by the following code snippet.
string s = "Happynewyear";
cout << s[0];
if you want to store the first character in a separate string,
string s = "Happynewyear";
string c = "";
c.push_back(s[0]);
cout << c;

Java strings are simply an array of char. So, char c = s[0] where s is string.

counting number of words after last occurrence of every word in an array of strings

i am working on text. I want to find the number of words after the last occurrence of a particular word in an array of strings.For instance,
String[] array={cat,rat,cat,bat,cat,cat,bat,fat,mat}
and I want to find the last occurrence of every word in this array and the number of words after the last occurrence .
How can I do it???

Iterate and count the array backwards and every new word that you encounter this way is the last or only instance of this word in the array. You can i.e. put the words in a hash set to check whether you have seen them already. Whenever you detect a new word this way you get the number of words behind it from the counter or by calculating array.length - currentPosition.

There is a solution with RegEx in DotNet if you will work with strings.
To search in an array here is an short example:
using System;
class Program
{
static void Main()
{
//
// Use this array of string references.
//
string[] array1 = { "cat", "dog", "carrot", "bird" };
//
// Find first element starting with substring.
//
string value1 = Array.Find(array1,
element => element.StartsWith("car", StringComparison.Ordinal));
//
// Find first element of three characters length.
//
string value2 = Array.Find(array1,
element => element.Length == 3);
//
// Find all elements not greater than four letters long.
//
string[] array2 = Array.FindAll(array1,
element => element.Length <= 4);
Console.WriteLine(value1);
Console.WriteLine(value2);
Console.WriteLine(string.Join(",", array2));
}
}
Also you can take a look to MSDN Example
Hope that helps
Regards

In Ruby:
arr = [:cat,:rat,:cat,:bat,:cat,:cat,:bat,:fat,:mat]
hash = {}
arr.reverse.each_with_index {|item, index| hash[item]=index unless hash.has_key?(item)}
hash
=> {:mat=>0, :fat=>1, :bat=>2, :cat=>3, :rat=>7}

How to Use Indexof()method in java

I am using indexof() for finding a sub string. It finds my string if my string is not on first position, if my string is at the first location it won't work. Can any one suggest another way to find it?
Here is My Code:-
public class IndexOfStr {
public static void main(String args[]) {
String s = "Niraj";
System.out.println(s);
System.out.println("indexOf(niraj, 1) -> " + s.indexOf("niraj", 1));
}}
Output:-
Niraj indexOf(niraj, 1) -> -1
I am trying to to find the string in my Excel file.

The first character in a strings is at index 0, not index 1.
Do also note that indexOf is case sensitive.
I don't know how you have access to the data in the Excel file, but you probably want to either convert all data to lower case when you search for a match, or use regexp when searching, and make the regexp case insensitive.

from docs:
Returns the index within this string of the first occurrence of the
specified substring, starting at the specified index. The integer
returned is the smallest value k for which:
k >= Math.min(fromIndex, this.length()) && this.startsWith(str,
k) If no such value of k exists, then -1 is returned.
You started from index 1 instead of index 0, so the string was not found.
You can do either s.indexOf("niraj", 0) or s.indexOf("niraj")

You should start from 0 rather than 1.
s.indexOf("Niraj", 0);
and please keep in mind that indexOf() method is case-sensitive.

Two errors occur here:
1) Your string is "Niraj", and you would like to find substring "niraj". Therefore, your substring does not exist in the given string and you get -1.
2) You start searching at position 1, not position 0, therefore your substring is not in the given range.
Either enter correct substring or call
s.toLowerCase().indexOf("niraj", 0)