Compilare: user.cpp: In function ‘void dfs(int, int)’: user.cpp:15:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[x].size();++i) ^ user.cpp: In function ‘void dfs2(int, int)’: user.cpp:24:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[x].size();++i) ^ user.cpp: In function ‘void dfs3(int)’: user.cpp:31:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[x].size();++i) ^ user.cpp:32:7: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(!use[v[x][i]]) ^