int index(const char * str1, const char * str2, int pos){    int i = pos;    int j = 0;       while(i < strlen(str1) && j < strlen(str2))       {               if(str1[i] ==  str2[j]) // matched then continue               {                          ++i;                          ++j;               }               else     // unmatched then backtrace               {                   i = i - j + 1;                   j = 0;               }       }       if(j >= strlen(str2))  // matched and return the index            return i-strlen(str2);       else            return -1;  // not found}

int index(char *t, char *p, int len1, int len2) {    int i, j;    for (i = 0; i < len1; i++) {        for (j = 0; j < len2; j++) {            if (p[j] != t[j + i]) {                break;            }        }        if (j == len2) {            return i;        }    }    return -1;}