foo.cc: In function 'void dfs(int, int)':
foo.cc:30:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0;i < son[x].size();++i) {
                    ~~^~~~~~~~~~~~~~~
foo.cc: In function 'void solve()':
foo.cc:43:9: error: 'dep' was not declared in this scope
     if (dep % 2) puts("Alice");
         ^~~