# Diameter of Binary Tree

Nov 24, 2017

Given a binary tree, you need to compute 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.

Example: Given a binary tree

      1
/ \
2   3
/ \
4   5


Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].

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

leftH = heightOfHeight(root->left)
rightH = heightOrHeight(root->right)
d = diameterOfBinaryTree(root->left) + diameterOfBinaryTree(root->right)
return max(d,leftH+rightH+2)


int diameterOfBinaryTree(TreeNode* root) {
int h;
return diameterOfBinaryTree(root,h);
}
int diameterOfBinaryTree(TreeNode *root,int &height) {
if (root == nullptr) {
height = -1;
return 0;
}
int leftH,rightH;
int leftD = diameterOfBinaryTree(root->left,leftH);
int rightD = diameterOfBinaryTree(root->right,rightH);

height = max(leftH,rightH) + 1;
return max(leftH + rightH + 2,max(leftD,rightD) );
}

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