gistfile1.txt

#include <iostream>

using namespace std;

unsigned strlen(const char *str) {
    const char *start = str;
    while ('\0' != *str) {
        ++str;
    }
    int l = str - start;
    return l;
}

int strstr(const char *text, const char *pattern) {
    const char *text1 = text; // копируем text в переменную
    const char *pattern1 = pattern; // копируем pattern в переменную

 //   cout << *text << "  " << text << endl;
 //   cout << *pattern << "  " << pattern << endl;

    int textlength = strlen(text); // длина text
    int patternlength = strlen(pattern); // длина pattern
    int position = 0; // указатель на начало паттерна в тексте

    if (patternlength == 0) {
 //       cout << "position=" << position;
        return position;
    }
 if (patternlength > textlength){
     return -1;
 }
    while ('\0' != *text) {
  //      cout << "*text=" << *text << "     " << "text=" << text << endl;
        if (*text == *pattern) {
            position = textlength - strlen(text);
//            cout << "position=" << position << endl;
            text++;
            pattern++;
                  if ('\0' == *pattern) {
                position = 1+position - patternlength;
//                cout << "end of pattern found, position=" << position << endl;
                return position;

            }
        }
        else {
            text++;
            position = -1;
            pattern = pattern1;
 //           cout << pattern << endl;
        }
    }

  //  cout << position << endl;
    return position;

}