From e8e70c2cf57ab9e1a1d13a3bd53ffb761fef7779 Mon Sep 17 00:00:00 2001
From: Mistivia <i@mistivia.com>
Date: Fri, 22 Aug 2025 16:43:08 +0800
Subject: solve 21

---
 src/bin/p0002.rs | 41 +-------------------------------------
 src/bin/p0021.rs | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs       |  1 +
 src/list.rs      | 40 +++++++++++++++++++++++++++++++++++++
 4 files changed, 102 insertions(+), 40 deletions(-)
 create mode 100644 src/bin/p0021.rs
 create mode 100644 src/lib.rs
 create mode 100644 src/list.rs

diff --git a/src/bin/p0002.rs b/src/bin/p0002.rs
index ac028a2..d8acf94 100644
--- a/src/bin/p0002.rs
+++ b/src/bin/p0002.rs
@@ -1,18 +1,4 @@
-#[derive(PartialEq, Eq, Clone, Debug)]
-pub struct ListNode {
-  pub val: i32,
-  pub next: Option<Box<ListNode>>
-}
-
-impl ListNode {
-  #[inline]
-  fn new(val: i32) -> Self {
-    ListNode {
-      next: None,
-      val
-    }
-  }
-}
+use leetcode::list::*;
 
 struct Solution {}
 
@@ -54,31 +40,6 @@ impl Solution {
     }
 }
 
-fn vector2list(vec: Vec<i32>) -> Option<Box<ListNode>> {
-    let mut result: Option<Box<ListNode>> = None;
-    for i in 0..vec.len() {
-        let mut new_result = Some(Box::new(ListNode::new(vec[vec.len() - i - 1])));
-        new_result.as_mut().unwrap().next = result;
-        result = new_result;
-    }
-    result
-}
-
-fn list2vector(lst: Option<Box<ListNode>>) -> Vec<i32> {
-    let mut result: Vec<i32> = Vec::new();
-    let mut cur = &lst;
-    loop {
-        match cur {
-            None => break,
-            Some(node) => {
-                result.push(node.val);
-                cur = &node.next;
-            },
-        }
-    }
-    result
-}
-
 fn test(l1: Vec<i32>, l2: Vec<i32>) -> Vec<i32> {
     list2vector(Solution::add_two_numbers(vector2list(l1), vector2list(l2)))
 }
diff --git a/src/bin/p0021.rs b/src/bin/p0021.rs
new file mode 100644
index 0000000..d0ce9e6
--- /dev/null
+++ b/src/bin/p0021.rs
@@ -0,0 +1,60 @@
+use leetcode::list::*;
+
+impl Solution {
+    pub fn merge_two_lists(list1: Option<Box<ListNode>>, list2: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        let mut p1 = &list1;
+        let mut p2 = &list2;
+        let mut result: Vec<i32> = vec!();
+        loop {
+            let v1: i32;
+            let v2: i32;
+            match p1 {
+                None => {
+                    match p2 {
+                        None => break,
+                        Some(px) => {
+                            result.push(px.val);
+                            p2 = &px.next;
+                            continue;
+                        }
+                    }
+                },
+                Some(p1) => { v1 = p1.val; },
+            }
+            match p2 {
+                None => {
+                    match p1 {
+                        None => break,
+                        Some(px) => {
+                            result.push(px.val);
+                            p1 = &px.next;
+                            continue;
+                        }
+                    }
+                },
+                Some(p2) => { v2 = p2.val; },
+            }
+            if v1 <= v2 {
+                result.push(v1);
+                p1 = match p1 {
+                    Some(px) => &px.next,
+                    None => p1,
+                };
+            } else {
+                result.push(v2);
+                p2 = match p2 {
+                    Some(px) => &px.next,
+                    None => p2,
+                };
+            }
+        }
+        vector2list(result)
+    }
+}
+
+struct Solution {}
+fn main() {
+    println!("{:?}", list2vector(
+        Solution::merge_two_lists(vector2list(vec!(1,3,5)),
+                                  vector2list(vec!(2,4,6)))));
+}
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..651aed7
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1 @@
+pub mod list;
\ No newline at end of file
diff --git a/src/list.rs b/src/list.rs
new file mode 100644
index 0000000..d033cfe
--- /dev/null
+++ b/src/list.rs
@@ -0,0 +1,40 @@
+#[derive(PartialEq, Eq, Clone, Debug)]
+pub struct ListNode {
+    pub val: i32,
+    pub next: Option<Box<ListNode>>
+}
+//
+impl ListNode {
+    #[inline]
+    pub fn new(val: i32) -> Self {
+        ListNode {
+            next: None,
+            val
+        }
+    }
+}
+
+pub fn vector2list(vec: Vec<i32>) -> Option<Box<ListNode>> {
+    let mut result: Option<Box<ListNode>> = None;
+    for i in 0..vec.len() {
+        let mut new_result = Some(Box::new(ListNode::new(vec[vec.len() - i - 1])));
+        new_result.as_mut().unwrap().next = result;
+        result = new_result;
+    }
+    result
+}
+
+pub fn list2vector(lst: Option<Box<ListNode>>) -> Vec<i32> {
+    let mut result: Vec<i32> = Vec::new();
+    let mut cur = &lst;
+    loop {
+        match cur {
+            None => break,
+            Some(node) => {
+                result.push(node.val);
+                cur = &node.next;
+            },
+        }
+    }
+    result
+}
\ No newline at end of file
-- 
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