Subtree of Another Tree

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.


+++++++++++++


class Solution {
    public boolean isSubtree(TreeNode s, TreeNode t) {
        if(s == null)
            return false;
         if (isSameTree(s, t))
             return true;

        return isSubtree(s.left,t) || isSubtree(s.right,t);
    }

    public boolean isSameTree(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 isSameTree(s.left,t.left) && isSameTree(s.right,t.right);
    }
}