# 面试题55 - II. 平衡二叉树
# 示例
示例 1:
给定二叉树 [3,9,20,null,null,15,7]
3
/ \
9 20
/ \
15 7
返回 true 。
示例 2:
给定二叉树 [1,2,2,3,3,null,null,4,4]
1
/ \
2 2
/ \
3 3
/ \
4 4
返回 false 。
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# JS
/**
* Definition for a binary tree node.
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
/**
* @param {TreeNode} root
* @return {boolean}
*/
var isBalanced = function (root) {
// 计算节点深度
const treeDeep = function (node, n=0) {
if (node) {
let left = treeDeep(node.left, n + 1)
let right = treeDeep(node.right, n + 1)
return left > right ? left : right
}
return n
}
// 层序遍历判断
const judge = function (node) {
if (!node) {
return true
}
let queue = []
queue.push(node)
while (queue.length !== 0) {
let n = queue.shift()
let l = treeDeep(n.left)
let r = treeDeep(n.right)
if (Math.abs(l - r) > 1) {
return false
}
if (n.left) {
queue.push(n.left)
}
if (n.right) {
queue.push(n.right)
}
}
return true
}
return judge(root)
};
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