958. 二叉树的完全性检验

给定一个二叉树，确定它是否是一个完全二叉树。

百度百科中对完全二叉树的定义如下：

若设二叉树的深度为 h，除第 h 层外，其它各层 (1～h-1) 的结点数都达到最大个数，第 h 层所有的结点都连续集中在最左边，这就是完全二叉树。（注：第 h 层可能包含 1~ 2h 个节点。）

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/check-completeness-of-a-binary-tree
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

class Solution {


    private Info solve(TreeNode root) {
        if (root == null) {
            return new Info(true, true, 0);
        }
        Info left = solve(root.left);
        Info right = solve(root.right);

        if (left.height == right.height) {
            return new Info(left.ok && right.ok && left.isFull, left.isFull && right.isFull, left.height + 1);
        } else if (left.height == right.height + 1) {
            return new Info(left.ok && right.ok && right.isFull, false, left.height + 1);
        } else {
            return new Info(false, false, Math.max(left.height, right.height) + 1);
        }
    }


    public boolean isCompleteTree(TreeNode root) {
        if (root == null) {
            return true;
        }
        return solve(root).ok;
    }
}

class Info {
    boolean ok;
    boolean isFull;
    int height;

    public Info(boolean ok, boolean isFull, int height) {
        this.ok = ok;
        this.isFull = isFull;
        this.height = height;
    }
}


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;
    }
}