add solution: same-tree

Author: dusunax

same-tree/dusunax.py

@@ -0,0 +1,37 @@
+'''
+# 100. Same Tree
+
+## Base case
+- if both nodes are None, return True
+- if one of the nodes is None, return False
+- if the values of the nodes are different, return False
+
+## Recursive case
+- check if the left subtrees are the same
+- check if the right subtrees are the same
+
+## Time and Space Complexity
+
+```
+TC: O(n)
+SC: O(n)
+```
+
+#### TC is O(n):
+- visiting each node once, balanced or skewed, it's O(n)
+
+#### SC is O(n):
+- for h is tree's height.
+  - in best case(balanced): h is logN, so SC is O(logN)
+  - in worst case(skewed): h is N, so SC is O(N)
+'''
+class Solution:
+    def isSameTree(self, p: Optional[TreeNode], q: Optional[TreeNode]) -> bool:
+        if not p and not q:
+            return True
+        if not p or not q:
+            return False
+        if p.val != q.val:
+            return False
+
+        return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right)