Compilare: main.cpp: In function 'bool ok(int)': main.cpp:11:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=j=0;j<st.size();j++) ~^~~~~~~~~~ main.cpp:16:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i==-1||v[st[j]-'a'].size()-i<nr) ~~~~~~~~~~~~~~~~~~~~~^~~ main.cpp: In function 'int main()': main.cpp:32:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(r==v[i].size()) ~^~~~~~~~~~~~~