Sum of paths in a binary tree

DIRECTORY.md

@@ -151,6 +151,7 @@
     * [Binary Search Tree](data_structures/binary_tree/binary_search_tree.py)
     * [Binary Search Tree Recursive](data_structures/binary_tree/binary_search_tree_recursive.py)
     * [Binary Tree Mirror](data_structures/binary_tree/binary_tree_mirror.py)
+    * [Binary Tree Path Sum](data_structures/binary_tree/binary_tree_path_sum.py)
     * [Binary Tree Traversals](data_structures/binary_tree/binary_tree_traversals.py)
     * [Fenwick Tree](data_structures/binary_tree/fenwick_tree.py)
     * [Inorder Tree Traversal 2022](data_structures/binary_tree/inorder_tree_traversal_2022.py)

data_structures/binary_tree/Binary tree path sum

@@ -0,0 +1,22 @@
+class Solution:
+    def pathSum(self, root: TreeNode, sum: int) -> int:
+
+        global result
+        result = 0
+
+        def dfs(node, target):
+            if node is None: return
+            find_path_from_node(node, target)
+            dfs(node.left, target)
+            dfs(node.right, target)
+
+        def find_path_from_node(node, target):
+            global result
+            if node is None: return
+            if node.val == target: result += 1
+            find_path_from_node(node.left, target-node.val)
+            find_path_from_node(node.right, target-node.val)
+
+        dfs(root, sum)
+
+        return result

data_structures/binary_tree/binary_tree_path_sum.py

@@ -0,0 +1,78 @@
+"""
+Given the root of a binary tree and an integer target, 
+find the number of paths where the sum of the values
+along the path equals target.
+
+
+Leetcode reference: https://leetcode.com/problems/path-sum-iii/
+"""
+
+from __future__ import annotations
+
+
+class Node:
+    """
+    A Node has data variable and pointers to Nodes to its left and right.
+    """
+
+    def __init__(self, data: int) -> None:
+        self.data = data
+        self.left: Node | None = None
+        self.right: Node | None = None
+
+
+class BinaryTreePathSum:
+    r"""
+    The below tree looks like this
+          10
+         /  \
+        5   -3
+       / \    \
+      3   2    11
+     / \   \
+    3  -2   1
+
+
+    >>> tree = Node(10)
+    >>> tree.left = Node(5)
+    >>> tree.right = Node(-3)
+    >>> tree.left.left = Node(3)
+    >>> tree.left.right = Node(2)
+    >>> tree.right.right = Node(11)
+    >>> tree.left.left.left = Node(3)
+    >>> tree.left.left.right = Node(-2)
+    >>> tree.left.right.right = Node(1)
+
+    >>> BinaryTreePathSum(tree).path_sum(8)
+    3
+    >>> BinaryTreePathSum(tree).path_sum(7)
+    1
+    >>> tree.right.right = Node(10)
+    >>> BinaryTreePathSum(tree).path_sum(8)
+    2
+    """
+
+    def __init__(self, tree: Node) -> None:
+        self.tree = tree
+
+    def depth_first_search(self, node: Node | None) -> int:
+        """
+
+        """
+        if node is None:
+            return 0
+
+        return self.depth_first_search(node)
+
+    def path_sum(self, target: int) -> int:
+        """
+
+
+        """
+        return self.depth_first_search(self.tree, target)
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()