Path Sum/ Path Sum II

Author: gavinfish

112 Path Sum.py

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+'''
+Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
+
+For example:
+Given the below binary tree and sum = 22,
+              5
+             / \
+            4   8
+           /   / \
+          11  13  4
+         /  \      \
+        7    2      1
+return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
+'''
+
+# Definition for a binary tree node.
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+class Solution(object):
+    def hasPathSum(self, root, sum):
+        """
+        :type root: TreeNode
+        :type sum: int
+        :rtype: bool
+        """
+        if not root:
+            return False
+        sum -= root.val
+        if sum == 0 and root.left is None and root.right is None:
+            return True
+        return self.hasPathSum(root.left, sum) or self.hasPathSum(root.right, sum)
+
+
+if __name__ == "__main__":
+    None

113 Path Sum II.py

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+'''
+Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.
+
+For example:
+Given the below binary tree and sum = 22,
+              5
+             / \
+            4   8
+           /   / \
+          11  13  4
+         /  \    / \
+        7    2  5   1
+return
+[
+   [5,4,11,2],
+   [5,8,4,5]
+]
+'''
+
+# Definition for a binary tree node.
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+class Solution(object):
+    def pathSum(self, root, sum):
+        """
+        :type root: TreeNode
+        :type sum: int
+        :rtype: List[List[int]]
+        """
+        result = []
+        self._pathSum(root, sum, [], result)
+        return result
+
+    def _pathSum(self, root, sum, curr, result):
+        if not root:
+            return
+        sum -= root.val
+        if sum == 0 and root.left is None and root.right is None:
+            result.append(curr + [root.val])
+        if root.left:
+            self._pathSum(root.left, sum, curr + [root.val], result)
+        if root.right:
+            self._pathSum(root.right, sum, curr + [root.val], result)
+
+
+if __name__ == "__main__":
+    None