Department list to tree_牛客题霸

Convert the department list to preorder traversal of the name of department tree

示例1

输入

[["d1", "d0", "IT"], ["d2", "d0", "RD"], ["d0", "", "The Company"], ["d3", "d0", "HR"]]

["The Company","HR","IT","RD"]

On each level of the department tree, departments are listed in alphabetical order of the name