diff --git a/problems/0111.二叉树的最小深度.md b/problems/0111.二叉树的最小深度.md
index 074a7165..0b2ec0f6 100644
--- a/problems/0111.二叉树的最小深度.md
+++ b/problems/0111.二叉树的最小深度.md
@@ -591,6 +591,7 @@ impl Solution {
     }
 
     // 迭代
+    // 需要 use std::collections::VecDeque;
     pub fn min_depth(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
         let mut res = 0;
         let mut queue = VecDeque::new();