判断二叉树是不是完全二叉树

import java.util.LinkedList;

/**
 * 判断二叉树是不是完全二叉树
 * <p>
 * 1)任何节点有右无左，不是完全二叉树
 * 2)从第一个左右节点不双全的的节点开始，后续节点全是叶子结点
 */
public class IsCompleteBT {

    public static boolean isCBT1(Node head) {
        if (head == null) {
            return true;
        }
        LinkedList<Node> queue = new LinkedList<>();
        // 是否遇到过左右两个孩子不双全的节点
        boolean leaf = false;
        Node l = null;
        Node r = null;
        queue.add(head);
        while (!queue.isEmpty()) {
            head = queue.poll();
            l = head.left;
            r = head.right;
            // 如果遇到了不双全的节点之后，又发现当前节点不是叶节点
            if ((leaf && (l != null || r != null)) || (l == null && r != null)) {
                return false;
            }
            if (l != null) {
                queue.add(l);
            }
            if (r != null) {
                queue.add(r);
            }
            if (l == null || r == null) {
                leaf = true;
            }
        }
        return true;
    }

    public static boolean isCBT2(Node head) {
        if (head == null) {
            return true;
        }
        return process(head).isCBT;
    }

    public static Info process(Node X) {
        if (X == null) {
            return new Info(true, true, 0);
        }
        Info leftInfo = process(X.left);
        Info rightInfo = process(X.right);
        int height = Math.max(leftInfo.height, rightInfo.height) + 1;
        boolean isFull = leftInfo.isFull && rightInfo.isFull && leftInfo.height == rightInfo.height;
        boolean isCBT = false;
        if (isFull) {
            isCBT = true;
        } else { // 以x为头整棵树，不满
            if (leftInfo.isCBT && rightInfo.isCBT) {
                if (leftInfo.isCBT && rightInfo.isFull && leftInfo.height == rightInfo.height + 1) {
                    isCBT = true;
                }
                if (leftInfo.isFull && rightInfo.isFull && leftInfo.height == rightInfo.height + 1) {
                    isCBT = true;
                }
                if (leftInfo.isFull && rightInfo.isCBT && leftInfo.height == rightInfo.height) {
                    isCBT = true;
                }
            }
        }
        return new Info(isFull, isCBT, height);
    }

    // 对每一棵子树，是否是满二叉树、是否是完全二叉树、高度
    public static class Info {

        public boolean isFull;

        public boolean isCBT;

        public int height;

        public Info(boolean full, boolean cbt, int h) {
            isFull = full;
            isCBT = cbt;
            height = h;
        }

    }

    public static class Node {

        public int value;

        public Node left;

        public Node right;

        public Node(int data) {
            this.value = data;
        }

    }

}

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