Count letters in String without using strlen()

Question

I created a program that the user enters a string. But i need to count how many letters are in the string. The problem is im not allowed to use the strlen()function. So i found some methods but they use pointers but im not allowed to use that yet as we havent learned it. Whats the best way to do this in a simple method? I also tried chars but i dont have luck with that either.

#include <iostream>

using namespace std;

string long;
string short;


int main()
{

        cout << "Enter long string";
        cin >> long;


        cout << "Enter short string";
        cin >> short;



    return 0;
}

I need to get the length of long and short and print it.

I am trying to use it without doing strlen as asked in some previous questions.

`long` and `short` are keywords that you can't (portably) use as variable names. — Wintermute, Apr 26 '15 at 22:26
possible duplicate of [C++ String Length?](http://stackoverflow.com/questions/905355/c-string-length) — Fabio says Reinstate Monica, Apr 26 '15 at 22:27
@sonicboom Sorry, I had misunderstood your question, I thought you had said that `strlen()` isn't allowed because it works with C-style strings, and you are using `std::string`. The answer I've linked explains that you can use `string::size()` or `string::length()` in this case. But now I understand you are not allowed to use those functions either. — Fabio says Reinstate Monica, Apr 26 '15 at 23:04

codingEnthusiast · Accepted Answer · 2015-04-26T22:38:40.527

3

Do you mean something like this?

//random string given

int length = 1;
while(some_string[length - 1] != '\0')
  length++;

Or if you don't want to count the \0 character:

int length = 0;
while(some_string[length] != '\0')
  length++;

edited Apr 26 '15 at 22:38

answered Apr 26 '15 at 22:27

codingEnthusiast

3,800
2
25
37

Im just getting 3 for the value of length after running this.. Its not accurate @naltipar – soniccool Apr 26 '15 at 22:29
If i enter 2, i get 3. – soniccool Apr 26 '15 at 22:32
I fixed it by subtracting 1 – soniccool Apr 26 '15 at 22:33
Read the updated version, I thought you wanted to include the `\0` character. – codingEnthusiast Apr 26 '15 at 22:34
@downvoter it's generally a good idea to explain why you downvote the answer. – codingEnthusiast Apr 26 '15 at 22:35
What is \0 ? What does it stand for. – soniccool Apr 26 '15 at 22:35
It is an extra character always stored in the end of the string, to denote its end. You might be setting a string to be 2 characters long, but `\0` is placed in the end, making it 3 character long. – codingEnthusiast Apr 26 '15 at 22:37
The one where i dont want to count \0 isnt working and the one above wont compile – soniccool Apr 26 '15 at 22:37
Normally, you never count the '\0' character, so the second solution should be preferred. Also in the first code the \0 seems to miss some single quotes to me. Oh, and the code some_string[lengt - 1] is dangerous and leads to an error in the second code. – Juergen Apr 26 '15 at 22:38
1

Your 2nd version accesses `some_string[-1]`. That can't be good. The first one doesn't get the length right. So, both are wrong. You're lucky to get up-votes. – juanchopanza Apr 26 '15 at 22:38
Yeah, I did some mistakes while editing the post, thanks for those comments – codingEnthusiast Apr 26 '15 at 22:40
It is just amazing, how one of the simplest coding peaces can be difficult to implement correctly ... It is a good example, why to use solid libraries. – Juergen Apr 26 '15 at 22:40
@Juergen It is actually trivial to implement correctly. What is hard is to match the efficiency of `strlen`. – juanchopanza Apr 26 '15 at 22:42
Sh*t happens at night. – codingEnthusiast Apr 26 '15 at 22:42

score 1 · Answer 2 · answered Apr 26 '15 at 22:39

1

You can count from the beginning and see until you reach the end character \0.

std::string foo = "hello";

int length = 0;
while (foo[++length] != '\0');

std::cout << length;

answered Apr 26 '15 at 22:39

allejo

2,076
4
25
40

score 1 · Answer 3 · answered Apr 26 '15 at 22:55

If you use standard cpp string object I think the best way to get length of your string is to use method:

long.size();

It gives you number of characters in string without end string character '\0'. To use it you must include string library :

#include <string>

If you decide to use char table you can try method from cin:

char long_[20];
cout << "Enter long string\n";
int l = cin.getline(long_,20).gcount(); 
cout << l << endl;

gcount()

Count letters in String without using strlen()

3 Answers3