## Count number of nodes in binary tree in Java

static int sum=0; public static int size(TreeNode root){ if(root==null) return sum; sum++; sum=size(root.left); sum=size(root.right); return sum; }

We have to just complete the function "size" which counts the number of nodes in binary tree. I have written the above code. It is giving wrong answer for some testcases. Please explain what is wrong in above code.

Here:

sum=size(root.left); sum=size(root.right);

You are computing **two** sums, to then throw away the first one!

You could go: `return size(root.left)+size(root.right) + 1`

instead.

There is **also** no point in using a **static field** `sum`

here. If at all, that should be a **local** variable within that recursive method! Respectively: simply `return 0`

for null, otherwise use the return I provided here. There is **no need** to for that `sum`

variable in the first place!

**Count full nodes in a Binary tree (Iterative and Recursive ,** c) Push right child of popped item to Queue, if available. Below is the implementation of this idea Duration: 6:31
Posted: Aug 20, 2017 Given a Binary tree, the task is to find the number of visible nodes in the given binary tree. A node is a visible node if, in the path from the root to the node N, there is no node with greater value than N’s, Examples: Input: 5 / \ 3 10 / \ / 20 21 1 Output: 4 Explanation: There are 4 visible nodes. They are: 5: In the path 5 -> 3, 5 is the highest node value.

You have not set `sum`

correctly when get data from child node

sum += size(root.left); sum += size(root.right);

I would advice you not use a global static variable to get the value when you want to do it recursively

static int sum=0; public static int size(TreeNode root){ if(root==null) return 0; int cnt = 0; cnt++; cnt += size(root.left); cnt += size(root.right); return cnt; }

**Number of leaf nodes in full binary tree,** and each branching step creates 2 new leaf nodes, and one leaf node turns into an internal node (for a net of +1 leaf in the tree). Algorithm – Count leaf nodes in a binary tree using Recursion. If the node is null then return 0. If both the left child and right child of the node is null then return 1. As this node is a leaf node of the tree. Call the countLeaves function for the left child of the node. Call the countLeaves

Try something like this:

public static int size(final TreeNode node) { if (null == node ) return 0; return 1 + size( node.left ) + size( node.right ); }

**How many nodes does a full binary tree with N leaves contain ,** How many leaf nodes are in a full binary tree? Algorithm: count number of nodes in a binary tree using java(Fig 1) Create local variable nNodes (signify the node count) nNodes initialized to 0; Visit the Level 0. visit all nodes in Level 0 and found only node A; nNodes increment by 1 [nNodes = 1] Go to Level 1 and visit all nodes in Level 1 Found node B, nNodes increment by 1 [nNodes = 2]

**Binary Tree Theorems,** How do you find the number of internal nodes in a binary tree? LeetCode – Count Complete Tree Nodes (Java) Given a complete binary tree, count the number of nodes. The solution to this problem can be as simple as the following: public int countNodes (TreeNode root) { if( root == null){ return 0; } return 1 + countNodes ( root. left) + countNodes ( root. right); } public int countNodes (TreeNode root) { if (root == null) { return 0; } return 1 + countNodes (root.left) + countNodes (root.right); }

**Program to count leaf nodes in a binary tree,** Here: sum=size(root.left); sum=size(root.right);. You are computing two sums, to then throw away the first one! You could go: return Previous Next If you want to practice data structure and algorithm programs, you can go through data structure and algorithm interview questions. This is 8th part of java binary tree tutorial. Java Binary tree tutorial: Binary tree in java Binary tree preorder traversal Binary tree postorder traversal Binary tree inorder traversal Binary tree level order traversal Binary tree spiral order

**Count number of nodes in binary tree in Java,** An iterative algorithm to get the total number of leaf nodes of binary tree. 1) if the root is null then return zero. 2) start the count with zero. 3) push the root into Stack. 4) loop until Stack is not empty. 5) pop the last node and push left and right children of the last node if they are not null. 6) increase the There are 3 things we can count: The total number of nodes; The number of leaf nodes; The number of internal nodes; Counting all nodes. The number of nodes in a binary tree is the number of nodes in the root’s left subtree, plus the number of nodes in its right subtree, plus one (for the root itself).