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.
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */public class Solution { public boolean isSubtree(TreeNode s, TreeNode t) { if (s == null && t != null) return false; if (s == null && t == null) return true; if (s != null && t == null) return false; if (s.val == t.val) { if (isGoOn(s, t)) return true; } return isSubtree(s.left, t) || isSubtree(s.right, t); } private boolean isGoOn(TreeNode s, TreeNode t) { if (s == null && t != null) return false; if (s == null && t == null) return true; if (s != null && t == null) return false; if (s.val == t.val) { return isGoOn(s.left, t.left) && isGoOn(s.right, t.right); } else return false; } }