/in/foo.cc: In function 'int main()':
/in/foo.cc:20:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = num; i < tree.size(); i++)
                    ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'void CreatTree(std::vector<Node>&, std::vector<Node>&)':
/in/foo.cc:34:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = n; i < tree.size(); i++)
                  ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'void Select(const std::vector<Node>&, int&, int&, int)':
/in/foo.cc:57:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for (i = 0; i < n; i++)
  ^~~
/in/foo.cc:63:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   for (int i = 0; i < n; i++)//找到次小权值的下标
   ^~~