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DiameterOfATree.java
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DiameterOfATree.java
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package Leetcode;
/**
* @author kalpak
*
* 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.
*/
public class DiameterOfATree {
static int result = 0;
public static int diameterOfBinaryTree(TreeNode root) {
dfsDiameterOfBinaryTree(root);
return result;
}
private static int dfsDiameterOfBinaryTree(TreeNode root) {
// Base Case
if(root == null)
return 0;
// Induction step: Get the left and right max path sum to compute the current max path sum
int leftHeight = Math.max(0, dfsDiameterOfBinaryTree(root.left));
int rightHeight = Math.max(0, dfsDiameterOfBinaryTree(root.right));
// update the result - longest path passes through a given node as the root node is left_height + right_height
result = Math.max(result, leftHeight + rightHeight);
// return back the best path, which is maximum.
// +1 for the current node
return 1 + Math.max(leftHeight, rightHeight);
}
public static void main(String[] args) {
TreeNode root= new TreeNode(1);
root.left = new TreeNode(2);
root.right = new TreeNode(3);
root.left.left = new TreeNode(4);
root.left.right = new TreeNode(5);
System.out.println(diameterOfBinaryTree(root));
}
}