another pointer exercise again

[etrusks]

Hi, i was dong next of my exercises and i kind of did it but again there were few questions that i was asking myself.
If someone has some free time and likes pointers you are welcome to help :D

Exercise:

Write a function char* findx(const char* s, const char* x )
that finds the first occurrence of the C-style string x in s

1. I couldn't figure out how can i actually return pointer to constant array. As far as i understand its not allowed to give pointers(that are not const) to constant arrays so i removed const from my function's argument list. (Maybe i misunderstood the exercise???)

2. Is there maybe a better way (faster) for getting this job done? (considering i did this exercise the way it was supposed to be done)

#include <iostream>
using namespace std;

char* findx(char* s, const char* x){
	//size of x
	int size_x = 0;
	while (x[size_x]){
		size_x++;
	}
	if (!size_x) return nullptr;

	//size of s
	int size_s = 0;
	while (s[size_s]){
		size_s++;
	}

	//looking for address of where x starts in s
	for (int i = 0; i < size_s; i++){			//scanning through s
		if (s[i] == x[0]){
			//if 1st char in "s" is the same as in "x" look for the rest
			int chars_found = 0;
			for (int j = 0; j < size_x; j++){
				if (s[i + j] != x[j]){ break; }
				else { chars_found++; }
			}
			//if found all the chars return starting address of this name in s
			if (chars_found == size_x) return &s[i]; 

		}
	}
	//if nothing was found return nullptr
	return nullptr;
}


int main(){

	char c_str[] = "Hello world!";
	char x[] = "world";

	char* p = findx(c_str, x);
	if (p){
		cout << p[0] << p[1] << p[2] << p[3] << p[4] << endl;
	}
	else cout << "its nullptr" << endl;

	system("pause");

}

[coder777]

You can write like so:

const char* findx(const char* s, const char* x){
[Edit]const char* p = findx(c_str, x);

As far as i understand its not allowed to give pointers(that are not const) to constant arrays

What do you mean by 'give pointers'?

2. Is there maybe a better way (faster) for getting this job done? (considering i did this exercise the way it was supposed to be done)

Yes, you don't need the size of the strings. The terminating '\0' suffice.

[xenovia12]

can you tell me, where did you get that exercises?

[etrusks]

Hey, thanks for answer!

What do you mean by 'give pointers'?

What i meant was : Not allowed to create non const pointer to constant array

[etrusks]

can you tell me, where did you get that exercises?

Sure thing man!
I'm reading B.Stroustrup's "Programming Principles and Practice Using C++" Second Edition :)

[xenovia12]

@etrusks, thanks,

it looks like there a logical error on your code, the content of your P pointer is world! not world

[fg109]

@Lorence30

I don't think that's a logic error. The p pointer is supposed to give the address in the original c-string that he finds the first occurrence of the search c-string. Since the original string is basically "Hello world!\0", then if you print it out starting from the first occurrence of world, you get "world!\0". (I included the null char because I think that makes it clearer.)