二叉树的中序遍历 - 久染的小世界呀

一.中序遍历

主要思路：用stack记录节点顺序，cur找到左子树的叶子节点，访问后出栈用cur指向父节点，接着访问右节点

方法一：非递归实现

let inorderTraversal = function(root){
    const result = []
    const stack = []
    let current = root
    while(current || stack.length){
        while(current){
            stack.push(current)
            current = current.left
        }
        current = stack.pop()
        result.push(current.val)
        current = current.right
    }
    return result
}

方法二：递归实现-最简单

let preorderTraversal = function(root){
    let result = []
    if(root){
        preorderTraversal(root.left)
        result.push(root.val)
        preorderTraversal(root.right)
    }
    return result;
}