Add problem 572

Author: avhn

algorithms/572/README.md

@@ -0,0 +1,47 @@
+## 572. Subtree of Another Tree
+
+Given two **non-empty** binary trees **s** and **t**, check whether tree **t** has exactly
+the same structure and node values with a subtree of **s**. A subtree of **s** is a tree
+consists of a node in **s** and all of this node's descendants. The tree s could also be
+considered as a subtree of itself.
+
+**Example 1:**
+
+Given tree s:
+```
+     3
+    / \
+   4   5
+  / \
+ 1   2
+```
+
+Given tree t:
+```
+   4 
+  / \
+ 1   2
+```
+Return **true**, because t has the same structure and node values with a subtree of s.
+
+<br>
+
+**Example 2:**
+Given tree s:
+```
+     3
+    / \
+   4   5
+  / \
+ 1   2
+    /
+   0
+```
+
+Given tree t:
+```
+   4
+  / \
+ 1   2
+```
+Return **false.**

algorithms/572/solution.go

@@ -0,0 +1,22 @@
+package main
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+func isSame(s *TreeNode, t *TreeNode) bool {
+	return s == nil && t == nil ||
+		s != nil && t != nil && s.Val == t.Val &&
+			isSame(s.Left, t.Left) && isSame(s.Right, t.Right)
+}
+
+// Time and space complexity: O(n) where n is size of the bigger tree
+func isSubtree(s *TreeNode, t *TreeNode) bool {
+	return s != nil &&
+		(isSame(s, t) || isSubtree(s.Left, t) || isSubtree(s.Right, t))
+}