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.
Example 2:
Given tree s:
3
/
4 5
/
1 2
/
0
Given tree t:
4 / 1 2
Return false.
1 /** 2 * Definition for a binary tree node. 3 * public class TreeNode { 4 * int val; 5 * TreeNode left; 6 * TreeNode right; 7 * TreeNode(int x) { val = x; } 8 * } 9 */ 10 public class Solution { 11 public boolean isSubtree(TreeNode s, TreeNode t) { 12 if (s == null) return false; 13 14 if (isSame(s, t)) return true; 15 return isSubtree(s.left, t) || isSubtree(s.right, t); 16 } 17 18 private boolean isSame(TreeNode s, TreeNode t) { 19 if (s == null && t == null) return true; 20 if (s == null || t == null) return false; 21 22 return s.val == t.val && 23 isSame(s.left, t.left) && 24 isSame(s.right, t.right); 25 } 26 }