Leetcode 113. Path Sum II

https://leetcode.com/problems/path-sum-ii/

Recursive DFS.

Solution:

# T:O(n) S:O(h)
class Solution:
    # @param root, a tree node
    # @param sum, an integer
    # @return a list of lists of integers
    def pathSum(self, root, sum):
        return self.pathSumRecu([], [], root, sum)
    
    def pathSumRecu(self, result, cur, root, sum):
        if root is None:
            return result
        
        if root.left is None and root.right is None and root.val == sum:
            result.append(cur + [root.val])
            return result
        
        cur.append(root.val)
        self.pathSumRecu(result, cur, root.left, sum - root.val)
        self.pathSumRecu(result, cur,root.right, sum - root.val)
        cur.pop()
        return result

Run Time: 84 ms