Compilare: main.cpp: In function 'int main()': main.cpp:34:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j<a[i].size(); ++j) ~^~~~~~~~~~~~ main.cpp:36:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (jj=j+1; jj<a[i].size(); ++jj) ~~^~~~~~~~~~~~