2096. Step-By-Step Directions From a Binary Tree Node to Another
## 思路
先找两个node的LCA, 再产生LCA到两点的路径
## Complexity
Time, Space: O(N)
## Code
```python
class Solution:
def getDirections(self, root: Optional[TreeNode], startValue: int,
destValue: int) -> str:
def find_lca(root, p, q):
if not root:
return None
if root.val == p or root.val == q:
return root
left = find_lca(root.left, p, q)
right = find_lca(root.right, p, q)
if left and right:
return root
return left or right
def get_path(root, p, path):
if not root:
return False
if root.val == p:
return True
path.append('L')
if get_path(root.left, p, path):
return True
path.pop()
path.append('R')
if get_path(root.right, p, path):
return True
path.pop()
return False
lca = find_lca(root, startValue, destValue)
res = []
get_path(lca, startValue, res)
res = ['U' for _ in range(len(res))]
get_path(lca, destValue, res)
return ''.join(res)
```