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; } * } */ class Solution { public boolean isSubtree(TreeNode s, TreeNode t) { if(s==null&&t==null) return true; if(s==null&&t!=null) return false; if(s!=null&&t==null) return false; return isSameTree(s,t)||isSubtree(s.left,t)||isSubtree(s.right,t); } public boolean isSameTree(TreeNode a, TreeNode b){ if(a==null&&b==null) return true; if(a==null&&b!=null) return false; if(a!=null&&b==null) return false; if(a.val!=b.val) return false; return isSameTree(a.left,b.left)&&isSameTree(a.right,b.right); } }
原文：https://www.cnblogs.com/hygeia/p/9789051.html