Compilare: main.cpp: In function 'int main()': main.cpp:21:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.length(); i++) { ~~^~~~~~~~~~~~ main.cpp:25:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < s.length()-1 && s[j+1] == s[j]) j++; ~~^~~~~~~~~~~~~~ main.cpp:26:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j-i+1 >= k && j < s.length()-1) nxt += s.substr(j+1, s.length()-j); ~~^~~~~~~~~~~~~~