lua实现树的先，中，后序遍历

function visitNode(data)
    print(data)
end

function Inorder(node)
    if node.left then
        node.left:traversal()
    end
    visitNode(node.data)
    if node.right then
        node.right:traversal()
    end
end

function Preorder(node)
    visitNode(node.data)
    if node.left then
        node.left:traversal()
    end
    if node.right then
        node.right:traversal()
    end
end

function Postorder(node)
    if node.left then
        node.left:traversal()
    end
    if node.right then
        node.right:traversal()
    end
    visitNode(node.data)
end

preorderTra = {__index = {traversal = Preorder}}    --先序遍历
inorderTra = {__index =  {traversal = Inorder}}     --中序遍历
postorderTra = {__index = {traversal = Postorder}}  --后序遍历


function create(tab)
    local t = tab
    setmetatable(t, preorderTra)
    return t
end

-- 创建一个二叉树
node1 = create({data = 1, left = nil, right = nil})
node2 = create({data = 2, left = nil, right = nil})
node3 = create({data = 3, left = node1, ritht = nil})
node4 = create({data = 4, left = nil, right = node2})
rootNode = create({data = 5, left = node3, right = node4})

-- roonode = create({data = 5})
-- roonode.left = create({data = 3})
-- roonode.right = create({data = 4})
-- roonode.left.left = create({data = 1})
-- rootNode.right.right = create({data = 2})

--遍历
rootNode:traversal()