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11 - diameter of binary tree.cpp
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11 - diameter of binary tree.cpp
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/*
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.
Example 1:
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].
Example 2:
Input: root = [1,2]
Output: 1
*/
//-------------------------------------O(N^2)-----------------------------------------------
class Solution {
private:
int height(TreeNode *root)
{
if(root == NULL)
return 0;
return max(height(root -> left),height(root -> right))+1;
}
void helper(TreeNode* root,int &maxi)
{
if(root == NULL)
return ;
int lh = height(root -> left);
int rh = height(root -> right);
maxi = max(lh+rh,maxi);
helper(root->left,maxi);
helper(root->right,maxi);
}
public:
int diameterOfBinaryTree(TreeNode* root) {
if(root == NULL)
return 0;
int maxi = INT_MIN;
helper(root,maxi);
return maxi;
}
};
//---------------------------------------O(N)------------------------------------------------
class Solution {
private:
int helper(TreeNode *root,int &maxi)
{
if(root == NULL)
return 0;
int lh = helper(root -> left,maxi);
int rh = helper(root -> right,maxi);
//Don't need to compute height again and again
maxi = max(lh+rh,maxi);
return max(lh,rh)+1;
}
public:
int diameterOfBinaryTree(TreeNode* root) {
if(root == NULL)
return 0;
int maxi = INT_MIN;
helper(root,maxi);
return maxi;
}
};