Subtree of another tree

Tree Depth-First Search String Matching Binary Tree Hash Function

51.3% acceptance

Jan 13, 2026

8865

601

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.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

// Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
//   pub val: i32,
//   pub left: Option<Rc<RefCell<TreeNode>>>,
//   pub right: Option<Rc<RefCell<TreeNode>>>,
// }
// 
// impl TreeNode {
//   #[inline]
//   pub fn new(val: i32) -> Self {
//     TreeNode {
//       val,
//       left: None,
//       right: None
//     }
//   }
// }
use std::rc::Rc;
use std::cell::RefCell;
impl Solution {
  pub fn is_subtree(root: Option<Rc<RefCell<TreeNode>>>, sub_root: Option<Rc<RefCell<TreeNode>>>) -> bool {
    fn same(a: &Option<Rc<RefCell<TreeNode>>>, b: &Option<Rc<RefCell<TreeNode>>>) -> bool {
      match (a, b) {
        (None, None) => true,
        (Some(x), Some(y)) => {
          let x = x.borrow(); let y = y.borrow();
          x.val == y.val && same(&x.left, &y.left) && same(&x.right, &y.right)
        }
        _ => false,
      }
    }
    fn check(root: &Option<Rc<RefCell<TreeNode>>>, sub: &Option<Rc<RefCell<TreeNode>>>) -> bool {
      match root {
        None => same(root, sub),
        Some(n) => {
          let n = n.borrow();
          same(root, sub) || check(&n.left, sub) || check(&n.right, sub)
        }
      }
    }
    check(&root, &sub_root)
  }
}