Compilare: main.cpp: In function 'void rec(int)': main.cpp:25:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j<a[i].size()&&fr[a[i][j]]==0) ~^~~~~~~~~~~~ main.cpp:27:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j==a[i].size()) continue; ~^~~~~~~~~~~~~ main.cpp:31:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j<a[i].size()&&fr[a[i][j]]==0) ~^~~~~~~~~~~~ main.cpp:33:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j==a[i].size()) { k--; continue; } ~^~~~~~~~~~~~~