Find the longest word in a String

Question

Following is my code:

 String LongestWord(String a)
{
    int lw=0;
    int use;
    String lon="";
    while (!(a.isEmpty()))
    {
        a=a.trim();
        use=a.indexOf(" ");
        if (use<0)
        {
            break;
        }
        String cut=a.substring(0,use);
        if(cut.length()>lw)
        {
            lon=cut;
        }
        lw=lon.length();
        a=a.replace(cut," ");
    }
    return lon;
}

The problem is that when I input a string like, "a boy is playing in the park"

it returns the longest word as "ying" because when it replaces 'cut' with " " for the first time, it removes all the 'a'-s too, such that it becomes " boy is pl ying in the p rk" after the first iteration of the loop

Please figure out what's wrong?

Thanks in advance!

Answer 1

You have already known the problem: the program does unwanted replacement.

Therefore, stop doing replacement. In this program, the word examined is directly cut instead of using the harmful replacement.

String LongestWord(String a)
{
    int lw=0;
    int use;
    String lon="";
    while (!(a.isEmpty()))
    {
        a=a.trim();
        use=a.indexOf(" ");
        if (use<0)
        {
            break;
        }
        String cut=a.substring(0,use);
        if(cut.length()>lw)
        {
            lon=cut;
        }
        lw=lon.length();
        a=a.substring(use+1); // cut the word instead of doing harmful replacement
    }
    return lon;
}

Answer 2

I would use arrays:

String[] parts = a.split(" ");

Then you can loop over parts, for each element (is a string) you can check length:

parts[i].length()

and find longest one.

Answer 3

I would use a Scanner to do this

String s = "the boy is playing in the parl";
int length = 0;
String word = "";
Scanner scan = new Scanner(s);
    while(scan.hasNext()){

        String temp = scan.next();
        int tempLength = temp.length();

        if(tempLength > length){
            length = tempLength;
            word = temp;
        }
    }
}

You check the length of each word, if it's longer then all the previous you store that word into the String "word"

Answer 4

You can use the split function to get an array of strings.

Than cycle that array to find the longest string and return it.

 String LongestWord(String a) {
    String[] parts = a.split(" ");
    String longest = null;
    for (String part : parts) {
        if (longest == null || longest.length() < part.length()) {
            longest = part;
        }
    }
    return longest;
 }

Answer 5

Another way uses Streams .

    Optional<String> max = Arrays.stream("a boy is playing in the park"
            .split(" "))
            .max((a, b) -> a.length() - b.length());
    System.out.println("max = " + max);

Answer 6

if you are looking for not trivial Solution ,you can solve it without using split or map but with only one loop

static String longestWorld(String pharagragh) {
    int maxLength = 0;
    String word=null,longestWorld = null;
    int startIndexOfWord = 0, endIndexOfWord;
    int wordLength = 0;
    for (int i = 0; i < pharagragh.length(); i++) {
        if (pharagragh.charAt(i) == ' ') {
            endIndexOfWord = i;
            wordLength = endIndexOfWord - startIndexOfWord;
            word = pharagragh.substring(startIndexOfWord, endIndexOfWord);
            startIndexOfWord = endIndexOfWord + 1;
            if (wordLength > maxLength) {
                maxLength = wordLength;
                longestWorld = word;
            }
        }
    }
    return longestWorld;
}

now lets test it

System.out.println(longestWorld("Hello Stack Overflow Welcome to Challenge World"));// output is Challenge

Answer 7

Try :

package testlongestword;

/**
 *
 * @author XOR
 */
public class TestLongestWord{
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        System.out.println(LongestWord("a boy is playing in the park"));
    }

    public static String LongestWord(String str){
        String[] words = str.split(" ");
        int index = 0;
        for(int i = 0; i < words.length; ++i){
            final String current = words[i];
            if(current.length() > words[index].length()){
                index = i;
            }
        }
        return words[index];
    }
}