Path sum

Tree Depth-First Search Breadth-First Search Binary Tree

54.5% acceptance

Feb 27, 2026

10661

1213

Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such that adding up all the values along the path equals targetSum. 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 has_path_sum(root: Option<Rc<RefCell<TreeNode>>>, target_sum: i32) -> bool {
    let Some(root_node) = root else { return false; };
    
    let mut stack = vec![(root_node, target_sum)];
    
    while let Some((node, remaining)) = stack.pop() {
      let node_borrow = node.borrow();
      let new_remaining = remaining - node_borrow.val;
      
      if node_borrow.left.is_none() && node_borrow.right.is_none() {
        if new_remaining == 0 {
          return true;
        }
        continue;
      }
      
      if let Some(left) = &node_borrow.left {
        stack.push((Rc::clone(left), new_remaining));
      }
      if let Some(right) = &node_borrow.right {
        stack.push((Rc::clone(right), new_remaining));
      }
    }
    
    false
  }
}