1448二叉树好节点

code

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var goodNodes = function(root) {
    let result = 0;
    function helper(root, max){
        if(root === null){
            return;
        }
        if(root.val >= max){
            result++;
            helper(root.left, root.val);
            helper(root.right, root.val);
        } else {
            helper(root.left, max);
            helper(root.right, max);
        }
    }
    helper(root, -Infinity);
    return result;
    
};

总结

1. 没啥特殊的感觉，跟层序遍历似乎是差不多的东西
2. 感觉不用看啥，一个值得注意的事情是根节点0的问题，老默认标成0忘带负数