陈越、何钦铭-数据结构作业11：TreeTraversalsAgain二叉树非递归遍历/栈遍历

Aninorderbinarytreetraversalcanbeimplementedinanon-recursivewaywithastack.Forexample,supposethatwhena6-nodebinarytree(withthekeysnumberedfrom1to6)istraversed,thestackoperationsare:push(1);push(2);push(3);pop();pop();push(4);pop();pop();push(5);push(6);pop();pop().Thenauniquebinary