Iterate on the characters in a string in Java without using any library function

Question

I want to find out the length of last word in a given string(a). A word is defined as a sequence of characters without a space(' '). The condition is not to use any of the library functions in doing this. I know its possible in C++. Can it be done in Java too? I did it using the following:

for(char c:a.toCharArray()) //this is not correct though. I need one without using an inbuilt method(considering its possible)

Is there a method that does not use the library functions?

edit:

Here is the solution in C++. Note it doesn't use a library function not even strlen() at any point.

class Solution {
public:
    int lengthOfLastWord(const string &s) {
        int len = 0;
        while (*s) {
            if (*s != ' ') {
                len++;
                s++;
                continue;
            }
            s++;
            if (*s && *s != ' ') len = 0;
        }
        return len;

    }};

What do you mean by library functions? If you can use `toCharArray()`, can you use `String.split()`? — Clark Kent, Apr 20 '16 at 13:57
Possible duplicate of [Fastest way to iterate over all the chars in a String](http://stackoverflow.com/questions/8894258/fastest-way-to-iterate-over-all-the-chars-in-a-string) — Akceptor, Apr 20 '16 at 13:58
The Java string library is pretty comprehensive... String.split(' ') returns an array that would do what you need. — Christopher Schneider, Apr 20 '16 at 13:59
My solution isn't correct. You can't call any of the inbuilt methods. — Abhishek Agarwal, Apr 20 '16 at 14:02
You will have to use some kind of library function to be able to access the individual characters of the string if you want to be able to find the last space in it. — Rabbit Guy, Apr 20 '16 at 14:03
@AbhishekAgarwal which "library" functions aren´t you allowed to use? The ones from `String`? — SomeJavaGuy, Apr 20 '16 at 14:04
@KevinEsche OP didn't specify. He just said no library functions. — Rabbit Guy, Apr 20 '16 at 14:05
Any inbuilt method of what? Because to manipulate a String, you will have to use String methods. The only way around it is to cheat and use reflection to access the private internal state of the String. But that would use plenty of methods of other classes than String. This exercise is pointless. — JB Nizet, Apr 20 '16 at 14:05
Also I just want to know IF its possible. If somehow we can work on a pointer level in Java? — Abhishek Agarwal, Apr 20 '16 at 14:10
No. Pointers are not a valid concept in java. Not like in C++ at least. — Rabbit Guy, Apr 20 '16 at 14:10
Your C++ doesn't compile, for many reasons... http://ideone.com/ueFCPr. You mean `const char*`, rather than `string`. — Andy Turner, Apr 20 '16 at 14:19

Andy Turner · Answer 1 · 2016-04-20T14:40:29.647

1

Your C++ code is invalid: you can't do pointer arithmetic on a reference. You could change the method signature type to:

int lengthOfLastWord(const char* s) {

and then it compiles and looks like it works (provided the array is null-terminated).

As such, roughly analogous code in Java would use a zero-terminated byte[]:

int longestWord(byte[] cs) {
  int len = 0;
  for (int i = 0; cs[i] != 0; i++) {
    // ...
  }
  return len;
}

edited Apr 20 '16 at 14:40

answered Apr 20 '16 at 14:33

Andy Turner

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Yeah. you are right. I wasn't focussing on the C++ code. Its been given on the site I was solving problems on. – Abhishek Agarwal Apr 20 '16 at 14:46

score 0 · Answer 2 · answered Apr 20 '16 at 13:59

0

Solution 1:

for (int i = 0, n = a.length(); i < n; i++) {
    char c = a.charAt(i);
}

Solution 2:

char[] chars = a.toCharArray();
for (int i = 0, n = chars.length; i < n; i++) {
    char c = chars[i];
}

answered Apr 20 '16 at 13:59

Akceptor

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score 0 · Answer 3 · answered Apr 20 '16 at 14:19

0

Here is a way to do:

String msg = "Hello everybody I'm Here";
String lastWord = msg.split(" ")[msg.split(" ").length-1];

System.out.println(lastWord);// "Here"

answered Apr 20 '16 at 14:19

poxen8

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Iterate on the characters in a string in Java without using any library function

3 Answers3