Suppose we have a binary tree, we have to check whether for every node in the tree except leaves, its value is same as the sum of its left child's value and its right child's value or not.
So, if the input is like
then the output will be True
To solve this, we will follow these steps −
Define a function dfs() . This will take root
if root is null, then
return True
if left of root is null and right of root is null, then
return True
left := 0
if left of root is not null, then
left := value of left of root
right := 0
if right of root is not null, then
right := value of right of root
return true when (left + right is same as value of root) and dfs(left of root) is true and dfs(right of root) is true
From the main method do the following −
return dfs(root)
Let us see the following implementation to get better understanding −
Example
class TreeNode: def __init__(self, data, left = None, right = None): self.val = data self.left = left self.right = right class Solution: def solve(self, root): def dfs(root): if root == None: return True if root.left == None and root.right == None: return True left = 0 if root.left: left = root.left.val right = 0 if root.right: right = root.right.val return (left + right == root.val) and dfs(root.left) and dfs(root.right) return dfs(root) ob = Solution() root = TreeNode(18) root.left = TreeNode(8) root.right = TreeNode(10) root.left.left = TreeNode(3) root.left.right = TreeNode(5) print(ob.solve(root))
Input
root = TreeNode(18) root.left = TreeNode(8) root.right = TreeNode(10) root.left.left = TreeNode(3) root.left.right = TreeNode(5)
Output
True