代码随想录算法刷题训练营day17

代码随想录算法刷题训练营day17：LeetCode(110)平衡二叉树

LeetCode(110)平衡二叉树
题目

代码

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode() {}*     TreeNode(int val) { this.val = val; }*     TreeNode(int val, TreeNode left, TreeNode right) {*         this.val = val;*         this.left = left;*         this.right = right;*     }* }*/
class Solution {public boolean isBalanced(TreeNode root) {//一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过 1 if(root==null){return true;}//一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过 1 //设置一个函数求求左右节点的高度差，并在求的过程中，判断左右节点的高度差int flagNode=betweenNodeHeight(root);if(flagNode==-1){return false;}else{return true;}}public int betweenNodeHeight(TreeNode root){if(root==null){return 0;}//后续遍历，先左子树，再右子树，再根-----一层一层往上返回-1；int leftHeight=betweenNodeHeight(root.left);if(leftHeight==-1){return -1;}int rightHeight=betweenNodeHeight(root.right);if(rightHeight==-1){return -1;}if(Math.abs(leftHeight-rightHeight)>1){return -1;}else{int rootHeight=Math.max(leftHeight, rightHeight)+1;return rootHeight;}}
}