LeetCode 110:
Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as:
a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example 1:
Given the following tree [3,9,20,null,null,15,7]:
3
/ \
9 20
/ \
15 7Return true.
Example 2:
Given the following tree [1,2,2,3,3,null,null,4,4]:
1
/ \
2 2
/ \
3 3
/ \
4 4
Return false.
采用后序遍历
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
static int x =[]()
{
std::ios::sync_with_stdio(false);
cin.tie(NULL);
return 0;
}();
class Solution {
public:
bool isBalanced(TreeNode* root) {
int depth = 0;
return ifBalanced(root,&depth);
}
private:
bool ifBalanced(TreeNode* root,int* depth)
{
if(root==nullptr)
{
*depth = 0;
return true;
}
int left,right;
if(ifBalanced(root->left,&left)&&ifBalanced(root->right,&right))
{
if(abs(left-right)<=1)
{
*depth = left>right?left+1:right+1;
return true;
}
}
return false;
}
};
