leetcode简单题25 N.112 路径总和 rust描述

use std::rc::Rc;
use std::cell::RefCell;
 
// Definition for a binary tree node.
#[derive(Debug, PartialEq, Eq)]
pub struct TreeNode {
    pub val: i32,
    pub left: Option>>,
    pub right: Option>>,
}
impl TreeNode {
    #[inline]
    pub fn new(val: i32) -> Self {
        TreeNode {
            val,
            left: None,
            right: None,
        }
    }
}
// 递归dfs
pub fn has_path_sum(root: Option>>, target_sum: i32) -> bool {
    fn dfs(node: &Option>>, target_sum: i32) -> bool {
        if let Some(node) = node {
            let node = node.borrow();
            let remaining_sum = target_sum - node.val;
            if node.left.is_none() && node.right.is_none() {
                return remaining_sum == 0;
            }
            dfs(&node.left, remaining_sum) || dfs(&node.right, remaining_sum)
        } else {
            false
        }
    }
 
    dfs(&root, target_sum)
}
// 迭代dfs
pub fn has_path_sum2(root: Option>>, target_sum: i32) -> bool {
    if root.is_none() {
        return false;
    }
 
    let mut stack = vec![(root.clone(), target_sum)];
 
    while let Some((node, remaining_sum)) = stack.pop() {
        if let Some(node) = node {
            let node = node.borrow();
            let new_sum = remaining_sum - node.val;
 
            if node.left.is_none() && node.right.is_none() && new_sum == 0 {
                return true;
            }
 
            if let Some(ref left) = node.left {
                stack.push((Some(Rc::clone(left)), new_sum));
            }
 
            if let Some(ref right) = node.right {
                stack.push((Some(Rc::clone(right)), new_sum));
            }
        }
    }
 
    false
}
use std::collections::VecDeque;
// bfs
pub fn has_path_sum3(root: Option>>, target_sum: i32) -> bool {
    if root.is_none() {
        return false;
    }
 
    let mut queue = VecDeque::new();
    queue.push_back((root.clone(), target_sum));
 
    while let Some((node, remaining_sum)) = queue.pop_front() {
        if let Some(node) = node {
            let node = node.borrow();
            let new_sum = remaining_sum - node.val;
 
            if node.left.is_none() && node.right.is_none() && new_sum == 0 {
                return true;
            }
 
            if let Some(ref left) = node.left {
                queue.push_back((Some(Rc::clone(left)), new_sum));
            }
 
            if let Some(ref right) = node.right {
                queue.push_back((Some(Rc::clone(right)), new_sum));
            }
        }
    }
 
    false
}
fn main() {}