Balanced Binary Tree 判断平衡二叉树

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.

 

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 Tree Depth-first Search

 

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int depth(TreeNode *node){
        if(node==NULL)
            return 0;
        int i=depth(node->left);
        int j=depth(node->right);
        return max(i,j)+1;
    }
    bool isBalanced(TreeNode *root) {
        if(root==NULL)
            return true;
        int leftDep=depth(root->left);
        int rightDep=depth(root->right);
        if(abs(leftDep-rightDep)<=1)
            return isBalanced(root->left) && isBalanced(root->right);
        else
            return false;
    }
};