Compilare: user.cpp: In function ‘int main()’: user.cpp:23:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<s.length(); ++i) { gf[s[i]-'a']+=1; cf[s[i]-'a']+=1; } ~^~~~~~~~~~~ user.cpp:28:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<s.length(); ++i) { ~^~~~~~~~~~~ user.cpp:31:6: warning: this ‘for’ clause does not guard... [-Wmisleading-indentation] for (char c = 'a'; c<='z'; ++c) ^~~ user.cpp:45:4: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘for’ if (sol.length()!=i+1) { okg=0; break; } ^~ user.cpp:45:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (sol.length()!=i+1) { okg=0; break; } ~~~~~~~~~~~~^~~~~