LeetCode 110. Balanced Binary Tr

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：判断一个二叉树，是不是平衡二叉树。

思路：递归遍历一棵树判断子树的树高，如果相差不超过1，那么就是平衡二叉树。

java代码：

public static boolean isBalanced(TreeNode root) {  
    if (root == null)  
        return true;  
    int distance = getDeep(root.left) - getDeep(root.right);  
  
    if (distance > 1 || distance < -1)  
        return false;  
    else  
        return isBalanced(root.left) && isBalanced(root.right);  
}  
  
// 最大深度  
public static int getDeep(TreeNode root) {  
    if (root == null)  
        return 0;  
    int level = 0;  
    LinkedList<TreeNode> list = new LinkedList<TreeNode>();  
    list.add(root);  
    int first = 0;  
    int last = 1;  
    while (first < list.size()) {  
        last = list.size();  
        while (first < last) {  
            if (list.get(first).left != null) {  
                list.add(list.get(first).left);  
            }  
            if (list.get(first).right != null) {  
                list.add(list.get(first).right);  
            }  
            first++;  
        }  
        level++;  
    }  
    return level;  
}