Path sum ii

Backtracking Tree Depth-First Search Binary Tree

61.8% acceptance

Feb 27, 2026

8586

170

Given the root of a binary tree and an integer targetSum, return all root-to-leaf paths where the sum of the node values in the path equals targetSum. Each path should be returned as a list of the node values, not node references. A root-to-leaf path is a path starting from the root and ending at any leaf node. 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 path_sum(root: Option<Rc<RefCell<TreeNode>>>, target_sum: i32) -> Vec<Vec<i32>> {
    let mut result = Vec::new();
    let mut path = Vec::new();
    
    fn dfs(node: Option<Rc<RefCell<TreeNode>>>, target: i32, path: &mut Vec<i32>, result: &mut Vec<Vec<i32>>) {
      if let Some(n) = node {
        let n_borrow = n.borrow();
        path.push(n_borrow.val);
        let remaining = target - n_borrow.val;
        
        if n_borrow.left.is_none() && n_borrow.right.is_none() && remaining == 0 {
          result.push(path.clone());
        } else {
          dfs(n_borrow.left.clone(), remaining, path, result);
          dfs(n_borrow.right.clone(), remaining, path, result);
        }
        
        path.pop();
      }
    }
    
    dfs(root, target_sum, &mut path, &mut result);
    result
  }
}