# Sum of alternate leaf nodes in bst in typescript

Ts program for Sum of alternate leaf nodes in bst. Here mentioned other language solution.

``````// TypeScript program for
// Sum of alternate leaf nodes in bst
class TreeNode
{
public data: number;
public left: TreeNode;
public right: TreeNode;
constructor(data: number)
{
this.data = data;
this.left = null;
this.right = null;
}
}
class BinarySearchTree
{
public root: TreeNode;
public alternate: boolean;
constructor()
{
this.root = null;
this.alternate = false;
}
// Insert a new node element
{
// Create a new node
var node = new TreeNode(data);
if (this.root == null)
{
// When add first node in bst
this.root = node;
}
else
{
var find = this.root;
// Add new node to proper position
while (find != null)
{
if (find.data >= data)
{
if (find.left == null)
{
// When left child empty
// So add new node here
find.left = node;
return;
}
else
{
// Otherwise
// Visit to left sub-tree
find = find.left;
}
}
else
{
if (find.right == null)
{
// When right child empty
// So add new node here.
find.right = node;
return;
}
else
{
// Visit to right sub-tree
find = find.right;
}
}
}
}
}
public number leafSum(node: TreeNode)
{
if (node != null)
{
if (node.left == null && node.right == null)
{
// Case A
// When node is leaf node.
// Change status.
this.alternate = !this.alternate;
// Check node is alternate or not.
if (this.alternate)
{
// When get alternate node.
return node.data;
}
}
else
{
// Case B
// When node is internal
// Visit left and right subtree and
// Find alternate node.
return this.leafSum(node.left) +
this.leafSum(node.right);
}
}
return 0;
}
public number alternateLeafSum()
{
// Reset alternate leaf node status
this.alternate = false;
return this.leafSum(this.root);
}
public static main()
{
var tree = new BinarySearchTree();
/*
Binary search tree
-------------------
5
/  \
/    \
/      \
3        19
/ \     /   \
2   4   8     31
/ \    / \
7   15 25  50
*/
// Test
console.log(tree.alternateLeafSum());
}
}
BinarySearchTree.main();
/*
file : code.ts
tsc --target es6 code.ts
node code.js
*/``````

Output

``34``

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