Published Aug 18, 2020
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The diameter of a binary tree is the length of the longest path between any two nodes in a tree. The length of path between two nodes is represented by the number of edges between them.
1
/ \
2 3 / \ 4 5
Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].
There are some related things: the height of a node. The height of a node is the number of edges on the longest path from the node to a leaf.
So we can find the left child height and right child height, and use them to find the diameter.
/**
* 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 diameter = 0;
public:
int diameterOfBinaryTree(TreeNode* root) {
height(root);
return diameter;
}
private:
int height(TreeNode* node) {
if (node == nullptr) {
return 0;
}
auto leftHeight = height(node->left);
auto rightHeight = height(node->right);
diameter = max(diameter, leftHeight + rightHeight);
return max(leftHeight, rightHeight) + 1;
}
};