958. Check Completeness of a Binary Tree

• 题目来源

题目来源

• C++代码实现

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution
{
public:
    bool isCompleteTree(TreeNode* root)
    {
        if(root == NULL)
		{
			return true;
		}

		return Sequencetraversal(root);
    }
private:
    bool Sequencetraversal(TreeNode* root)
	{
		queue<TreeNode*> dataqueue;
		TreeNode* l = NULL;
		TreeNode* r = NULL;
		bool leaf = false;

		dataqueue.push(root);

		while(!dataqueue.empty())
		{
			root = dataqueue.front();
			dataqueue.pop();
			l = root->left;
			r = root->right;

			/*一个节点有右孩子没有左孩子,则必不是完全二叉树*/
			if(root->right != NULL && root->left == NULL)
			{
				return false;
			}

			// leaf = true 则表示开启了叶节点的判断
			//
			if(leaf && (r != NULL || l != NULL) )
			{
				return false;
			}

			if(l != NULL)
			{
				dataqueue.push(root->left);
			}

			if(r != NULL)
			{
			    dataqueue.push(root->right);
			}
			else
			{
				leaf = true;  //有右孩子没有左孩子 开启叶节点的判断
			}
		}

        return true;
	}

};