93. 平衡二叉树
给定一个二叉树,确定它是高度平衡的。对于这个问题,一棵高度平衡的二叉树的定义是:一棵二叉树中每个节点的两个子树的深度相差不会超过1。
样例
给出二叉树 A={3,9,20,#,#,15,7}
, B={3,#,20,15,7}
A) 3 B) 3 / \ \ 9 20 20 / \ / \ 15 7 15 7
二叉树A是高度平衡的二叉树,但是B不是
/**
* Definition of TreeNode:
* class TreeNode {
* public:
* int val;
* TreeNode *left, *right;
* TreeNode(int val) {
* this->val = val;
* this->left = this->right = NULL;
* }
* }
*/
class Solution {
public:
/*
* @param root: The root of binary tree.
* @return: True if this Binary tree is Balanced, or false.
*/
bool isBalanced(TreeNode *root) {
// write your code here
// write your code here
return isSubTreeBalanced(root) != -1;
}
int isSubTreeBalanced(TreeNode *root) {
if(root == NULL) {
return 0;
}
int left = isSubTreeBalanced(root->left);
int right = isSubTreeBalanced(root->right);
if(left == -1 || right == -1 || abs(left - right) > 1) {
return -1;
}
else {
return (left > right ? left : right) + 1;
}
}
};