balancedBinaryTree.java

//判断一个二叉树是否为平衡二叉树
//递归求出左子树和右子树的高度，然后判断其值是否相差1

/**
 * Definition for binary tree
 * public class TreeNode {
 * int val;
 * TreeNode left;
 * TreeNode right;
 * TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
 int treeDepth(TreeNode root) {
 if(root==null) {
 return 0;
 }
 int leftDepth = treeDepth(root.left);
 int rightDepth = treeDepth(root.right);
 return Math.max(leftDepth + 1, rightDepth + 1);
 }
 
 public boolean isBalanced(TreeNode root) {
 if(root==null||(root.left==null&&root.right==null)) {
 return true;
 }
 int leftDep = treeDepth(root.left);
 int rightDep = treeDepth(root.right);
 int tmp = leftDep - rightDep;
 return ((tmp>=-1&&tmp<=1)&&isBalanced(root.left)&&isBalanced(root.right));
 
 }
}