/**

* 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} p

* @param {TreeNode} q

* @return {boolean}

*/

var isSameTree = function (p, q) {

// 递归退出

if (p === null && q === null) {

return true

} if (p === null || q === null) {

// 其中一个空了

return false

}

// 节点值相同

if (p.val !== q.val) {

return false

}

// 递归子节点

return isSameTree(p.left, q.left) && isSameTree(p.right, q.right)

}