Cinte's Leetcode Record
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958. 二叉树的完全性检验

Posted on Edited on In Disqus:
Symbols count in article: 1.7k Reading time ≈ 2 mins.

958. 二叉树的完全性检验

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isCompleteTree(TreeNode* root) {
        queue<TreeNode*> q;
        q.push(root);
        int expect = 1;
        while(!q.empty())
        {
            int sz = q.size();
            if(sz != expect)
                break;
            expect <<= 1;
            bool broke = false;
            for(int i = 0; i < sz; ++i)
            {
                auto p = q.front();
                q.pop();
                if(broke && (p->left || p->right)) // 前面断裂了，如果下一层还不是最后一层，那没了啊
                    return false;
                if(!p->left && p->right)
                    return false;
                if(!p->right) // 出现了断层，如果不是最后一层，那你g了
                    broke = true;
                if(p->left)
                    q.push(p->left);
                if(p->right)
                    q.push(p->right);
            }
        }
        while(!q.empty())
        {
            auto p = q.front();
            q.pop();
            if(p->left || p->right)
                return false;
        }
        return true;
    }
};

也算是层序

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isCompleteTree(TreeNode* root) {
        queue<TreeNode*> q;
        int i = 1;
        q.push(root);
        bool isBlock = false;
        while(!q.empty())
        {
            auto p = q.front();
            q.pop();
            if(!p)
            {
                isBlock = true;
                continue;
            }
            if(isBlock)
                return false;
            q.push(p->left);
            q.push(p->right);
        }
        return true;
    }
};