Cinte's Leetcode Record
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662. 二叉树最大宽度

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

662. 二叉树最大宽度

只要记录下来pos就没啥大问题

bfs
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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:
    int widthOfBinaryTree(TreeNode* root) {
        if(!root)
            return 0;
        queue<Node> q;
        int ret = 1;
        q.push(Node(root, 1));
        while(!q.empty())
        {
            long left = q.front().pos;
            for(int i = 0, sz = q.size(); i < sz; ++i)
            {
                auto p = q.front();
                q.pop();
                if(p.node->left)
                    q.push(Node(p.node->left, 2 * p.pos));
                if(p.node->right)
                    q.push(Node(p.node->right, 2 * p.pos + 1));
                if(i == sz - 1)
                    ret = max(ret, (int)(p.pos - left + 1));
            }
        }
        return ret;
    }
private:
    struct Node
    {
        TreeNode* node;
        long pos;
        Node(TreeNode* node, int pos) : node(node), pos(pos) {}
    };
};
dfs
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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:
    int widthOfBinaryTree(TreeNode* root) {
        if(!root)
            return 0;
        dfs(std::move(Node(root, 1)), 0);
        return ret;
    }
private:
    unordered_map<int, int> left;
    int ret{ 1 };
    struct Node
    {
        TreeNode* node;
        long pos;
        Node(TreeNode* node, int pos) : node(node), pos(pos) {}
    };
private:
    void dfs(Node node, int depth)
    {
        if(!left.count(depth))
            left.emplace(depth, node.pos);
        else
            ret = max(ret, int(node.pos - left[depth]) + 1);
        if(node.node->left)
            dfs(std::move(Node(node.node->left, node.pos * 2)), depth + 1);
        if(node.node->right)
            dfs(std::move(Node(node.node->right, node.pos * 2 + 1)), depth + 1);
    }
};