144. 二叉树的前序遍历

//前序遍历：根左右
var preorderTraversal = function(root) {let arr=[]const dfs=function(root){if(root==null){return}//根arr.push(root.val)//左dfs(root.left)//右dfs(root.right)}dfs(root)return arr
};

145. 二叉树的后序遍历

//后续遍历:左右根
var postorderTraversal = function(root) {let arr=[]const dfs=function(root){if(root===null){return}//左dfs(root.left)//右dfs(root.right)//根arr.push(root.val)}dfs(root)return arr
};

94. 二叉树的中序遍历

//中序遍历：左根右
var inorderTraversal = function(root) {let arr=[]const dfs=function(root){if(root==null){return}//左dfs(root.left)//根arr.push(root.val)//右dfs(root.right)}dfs(root)return arr
};