Accepted O(n) Java solution


  • 0
    B

    Diameter of a tree is the maximum of:
    (a.) Diameter of left subtree
    (b.) Diameter of right subtree
    (c.) (a.) + (b.) which passes through the root
    Diameter of a tree with single node is 0 if you consider diameter as edge count and 1 if you consider diameter as node count.

    class Solution {
       public int maxDiameter = 0;
       
       public int diameterOfBinaryTree(TreeNode root) {
          if(root == null) return 0;
          height(root);
          return maxDiameter;
       }
       
       public int height(TreeNode root) {
            if(root == null) return 0;
            int leftHeight = height(root.left);
            int rightHeight = height(root.right);
            maxDiameter = Math.max(maxDiameter, leftHeight + rightHeight);
            return Math.max(leftHeight, rightHeight) + 1;
       }
    
    }
    

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