572. Subtree of Another Tree

Given the roots of two binary trees root and subRoot, return true if there is a subtree of root with the same structure and node values of subRoot and false otherwise.

A subtree of a binary tree tree is a tree that consists of a node in tree and all of this node's descendants. The tree tree could also be considered as a subtree of itself.

Example 1:

Input: root = [3,4,5,1,2], subRoot = [4,1,2]
Output: true

Example 2:

Input: root = [3,4,5,1,2,null,null,null,null,0], subRoot = [4,1,2]
Output: false

Constraints:

• The number of nodes in the root tree is in the range [1, 2000].

• The number of nodes in the subRoot tree is in the range [1, 1000].

• -104 <= root.val <= 104

• -104 <= subRoot.val <= 104

Solution

Adapt the method of 100. same tree to recursively check the status

class Solution {
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        if(root == null && subRoot != null) return false;
        if(isSameTree(root, subRoot)) return true;
        return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
    }
    
    public boolean isSameTree(TreeNode node1, TreeNode node2){
        
        if(node1 == null && node2 == null) return true;
        if(node1 == null || node2 == null) return false;
        if(node1.val != node2.val) return false;
        return isSameTree(node1.left, node2.left) && isSameTree(node1.right, node2.right);   
        
    }
    
}