LeetCode 572. Subtree of Another Tree

Description

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.

Solution

也是对每一个结点都以其为头结点进行判断。

/**
 * 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)
            return false;
        return isSubtreeWithStart(s, t) || isSubtree(s.left, t) || isSubtree(s.right, t);
    }
    
    private boolean isSubtreeWithStart(TreeNode s, TreeNode t){
        if(s == null && t == null)
            return true;
        if(s == null || t == null)
            return false;
        if(s.val != t.val)
            return false;
        return isSubtreeWithStart(s.left, t.left) && isSubtreeWithStart(s.right, t.right);
    }
}

 

来源：CSDN

作者：jxnu_毛毛

链接：https://blog.csdn.net/weixin_41317766/article/details/104154988