572. Subtree of Another Tree

LeetCode

if t is a subtree of s:

  • s and t is same
  • t is a subtree of the left subtree of s
  • t is a subtree of the right subtree of s
/**
 * 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 isSame(s, t) || isSubtree(s.left, t) || isSubtree(s.right, t);
    }

    public boolean isSame(TreeNode s, TreeNode t) {
        if (s == null && t == null) {
            return true;
        }
        if (s == null || t == null) {
            return false;
        }
        return (s.val == t.val) && isSame(s.left, t.left) && isSame(s.right, t.right);
    }
}