Compilare: main.cpp: In function 'int main()': main.cpp:22:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<strlen(s); i++) ~^~~~~~~~~~ main.cpp:24:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i && n != strlen(s)) l[s[i] - 'a' + 1].push_back(n); ~~^~~~~~~~~~~~ main.cpp:41:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] { for(int i=0; i<l[ch].size(); i++) ~^~~~~~~~~~~~~