LeetCode: Balanced Binary Tree [110]

【题目】

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.

【题意】

判断二叉树是否是平衡二叉树

【思路】

平衡二叉树要求任意一个节点的左右子树高度差的绝对值不大于1.

按照定义，递归求解即可。

【代码】

/**
 * 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 getHeight(TreeNode *root){
        if(root==NULL)return 0;

        //获得左子树高度
        int leftHeight=getHeight(root->left);
        if(leftHeight==-1)return -1;
        //获得右子树高度
        int rightHeight=getHeight(root->right);
        if(rightHeight==-1)return -1;

        //判断左右子树高度差是否符合要求, 如果符合要求，则返回当前二叉树的高，如果不符合要求，则返回-1
        if(abs(leftHeight-rightHeight)<=1)
            return max(leftHeight, rightHeight)+1;

        return -1;
    }

    bool isBalanced(TreeNode *root) {
        if(root==NULL)return true;

        int height=getHeight(root);
        if(height==-1)return false;
        return true;

    }
};

LeetCode: Balanced Binary Tree [110]