Update 0112.路径总和.md

problems/0112.路径总和.md

@@ -1217,6 +1217,8 @@ object Solution {
 
 ### 112.路径总和.md
 
+递归：
+
 ```rust
 use std::rc::Rc;
 use std::cell::RefCell;
@@ -1235,6 +1237,38 @@ impl Solution {
 }
 ```
 
+迭代：
+
+```rust
+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 mut stack = vec![];
+        if let Some(node) = root {
+            stack.push((node.borrow().val, node.to_owned()));
+        }
+        while !stack.is_empty() {
+            let (value, node) = stack.pop().unwrap();
+            if node.borrow().left.is_none() && node.borrow().right.is_none() && value == target_sum
+            {
+                return true;
+            }
+            if node.borrow().left.is_some() {
+                if let Some(r) = node.borrow().left.as_ref() {
+                    stack.push((r.borrow().val + value, r.to_owned()));
+                }
+            }
+            if node.borrow().right.is_some() {
+                if let Some(r) = node.borrow().right.as_ref() {
+                    stack.push((r.borrow().val + value, r.to_owned()));
+                }
+            }
+        }
+        false
+    }
+```
+
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