Compilare: main.cpp: In function 'void df(int)': main.cpp:15:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<v[k].size();i++) { ~^~~~~~~~~~~~ main.cpp: In function 'void df2(int)': main.cpp:31:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<v[k].size();i++) { ~^~~~~~~~~~~~ main.cpp:47:49: warning: suggest parentheses around '&&' within '||' [-Wparentheses] } while (!st.empty() && !(a1==x && a2==k || a1==k && a2==x)); ~~~~~~^~~~~~~~