LeetCode-Daily-Question-33

Jul 20th 2022

7 月 20 日 每日一题

543. Diameter of Binary Tree

Given the root of a binary tree, return the length of the diameter of the tree.

The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

The length of a path between two nodes is represented by the number of edges between them.

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Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].

思路

It is similar to height of tree. Diameter = Height of the left subtree + Height of the right subtree. Keep track of the maxDiameter during traversal by an extra parameter and get the height of the tree.

代码

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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 diameterOfBinaryTree(TreeNode* root) {
        int diameter = 0;
        diaHelper(root, diameter);
        return diameter;
    }
    int diaHelper(TreeNode* node, int& diameter){
        if(!node)
            return 0;
        int left = diaHelper(node->left, diameter);
        int right = diaHelper(node->right, diameter);
        diameter = max(diameter, left + right);
        return max(left,right) + 1;
    }
};
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  1. 7 月 20 日 每日一题
    1. 543. Diameter of Binary Tree
    2. 思路
    3. 代码