Some_shit_searching_pattern_in_the_string

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>

using namespace std;

int strStr(const char *text, const char *pattern);
int strLen(const char *str);
bool strCheck(const char *p, const char *pattern);

int main()
{
	setlocale(0, "Russian");
	std::cout << "Programm started\n";

	struct test {
		int ret_value;
		const char *text;
		const char *pattern;
	};
	test tests[] = {
			{0, "", ""}, //0
			{0, "a", ""}, //1
			{0, "a", "a"}, //2
			{-1, "a", "b"}, //3
			{0, "aa", ""}, //4
			{0, "aa", "a"}, //5
			{0, "ab", "a"}, //6
			{1, "ba", "a"}, //7
			{-1, "bb", "a"}, //8
			{0, "aaa", ""}, //9
			{0, "aaa", "a"}, //10
			{1, "abc", "b"}, //11
			{2, "abc", "c"}, //12
			{-1, "abc", "d"}, //13
			{-1, "a", "aa"}, //14
			{-1, "a", "ba"}, //15
			{-1, "a", "ab"}, //16
			{-1, "a", "bb"}, //17
			{-1, "a", "aaa"}, //18
			{-1, "aa", "aaa"}, //19
			{0, "aaa", "aaa"}, //20
			{0, "aaab", "aaa"}, //21
			{1, "baaa", "aaa"}, //22
			{1, "baaaa", "aaa"}, //23
			{1, "baaab", "aaa"}, //24
			{-1, "abd", "abc"}, //25
			{2, "ababc", "abc"}, //26
			{3, "abdabc", "abc"}, //27
			{-1, "", "a"}, //28
			{2, "asasaf", "asaf"}, //29
			{2, "ababac", "abac"} //30
	};
	for (int i = 0; i < sizeof(tests) / sizeof(tests[0]); ++i) {
		int ret = strStr(tests[i].text, tests[i].pattern);
		(tests[i].ret_value == ret) ? cout << "OK" : cout << "Failed";
		cout << " : " << i << " (" << tests[i].ret_value << " : " << ret << ")" << endl;
	}

	system("pause");
	return 0;
}

//находит первое вхождение в строке text некоторого шаблона pattern
int strStr(const char *text, const char *pattern)
{
	if (*pattern == '\0')
		return 0;
	else if (*text == '\0')
		return -1;
	int N = strLen(text);
	for (int i = 0; i < N; i++)
	{
		if (strCheck(text + i, pattern))
			return i;
	}
	return -1;
}

//находит длину строки, не учитывая нулевой символ
int strLen(const char *str)
{
	int i = 0;
	while ( *(str + i) != '\0' )
		i++;
	return i;
}

//проверяет соответствие некоторой части строки шаблону
bool strCheck(const char *p, const char *pattern)
{
	for (; *pattern != '\0'; pattern++)
	{
		if (*p != *pattern)
			return false;
		p++;
	}
	return true;
}