Minimum depth of binary tree

Tree Depth-First Search Breadth-First Search Binary Tree

52.4% acceptance

Feb 27, 2026

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1365

Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. Note: A leaf is a node with no children.

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 min_depth(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
    use std::collections::VecDeque;
    let Some(root_node) = root else { return 0; };
    
    let mut queue = VecDeque::new();
    queue.push_back((root_node, 1));
    
    while let Some((node, depth)) = queue.pop_front() {
      let node_borrow = node.borrow();
      
      if node_borrow.left.is_none() && node_borrow.right.is_none() {
        return depth;
      }
      
      if let Some(left) = &node_borrow.left {
        queue.push_back((Rc::clone(left), depth + 1));
      }
      if let Some(right) = &node_borrow.right {
        queue.push_back((Rc::clone(right), depth + 1));
      }
    }
    
    0
  }
}