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IsBalanced55.java
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IsBalanced55.java
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package Leetcode;
public class IsBalanced55 {
/*Method: Recursion, Time: O(N^2), Space:O(N)**/
/**
计算节点高度的函数,即可判断二叉树是否平衡。
具体做法类似于二叉树的前序遍历,即对于当前遍历到的节点,
首先计算左右子树的高度,如果左右子树的高度差是否不超过 1,再分别递归地遍历左右子节点,并判断左子树和右子树是否平衡。
**/
public boolean isBalanced(TreeNode root) {
if(root == null) {
return true;
}
return Math.abs(getHeight(root.left) - getHeight(root.right)) <= 1 && isBalanced(root.left) && isBalanced(root.right);
}
private int getHeight(TreeNode node) {
if(node == null) {
return 0;
}
return Math.max(getHeight(node.left), getHeight(node.right)) +1;
}
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;
}
}
}