Compilare: main.cpp: In function 'int main()': main.cpp:18:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < str.size() && poz_start == -1; ++i) ~~^~~~~~~~~~~~ main.cpp:28:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = istart + 1; i < str.size(); ++i) ~~^~~~~~~~~~~~ main.cpp:25:14: warning: unused variable 'letterAppears' [-Wunused-variable] char letterAppears[124] = { 0 }; ^~~~~~~~~~~~~