From c3d977118be4e87ea20c0779540be3142ed34d88 Mon Sep 17 00:00:00 2001
From: jackfiled <xcrenchangjun@outlook.com>
Date: Fri, 24 May 2024 09:25:16 +0800
Subject: [PATCH] 20240524 Finished

---
 src/problem/mod.rs                        |  3 +-
 src/problem/p21_merge_two_sorted_lists.rs | 67 +++++++++++++++++++++++
 2 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 src/problem/p21_merge_two_sorted_lists.rs

diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index dbe297c..d4e1069 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -137,4 +137,5 @@ mod p452_minimum_number_of_arrows_to_burst_balloons;
 mod p71_simplify_path;
 mod p155_min_stack;
 mod p150_evaluate_reverse_polish_notation;
-mod p224_basic_calculator;
\ No newline at end of file
+mod p224_basic_calculator;
+mod p21_merge_two_sorted_lists;
\ No newline at end of file
diff --git a/src/problem/p21_merge_two_sorted_lists.rs b/src/problem/p21_merge_two_sorted_lists.rs
new file mode 100644
index 0000000..9709446
--- /dev/null
+++ b/src/problem/p21_merge_two_sorted_lists.rs
@@ -0,0 +1,67 @@
+/**
+ * [21] Merge Two Sorted Lists
+ */
+pub struct Solution {}
+
+use std::borrow::{Borrow, BorrowMut};
+
+use crate::util::linked_list::{ListNode, to_list};
+
+// submission codes start here
+
+// Definition for singly-linked list.
+// #[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
+//     }
+//   }
+// }
+impl Solution {
+    pub fn merge_two_lists(list1: Option<Box<ListNode>>, list2: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        let mut head = None;
+        let mut now = &mut head;
+
+        let (mut list1, mut list2) = (list1, list2);
+
+        *now = loop {
+            match (list1, list2) {
+                (Some(mut a), Some(mut b)) => {
+                    if a.val < b.val {
+                        list1 = a.next.take();
+                        list2 = Some(b);
+
+                        now = &mut now.insert(a).next;
+                    } else {
+                        list1 = Some(a);
+                        list2 = b.next.take();
+
+                        now = &mut now.insert(b).next
+                    }
+                },
+                (x, y) => break x.or(y)
+            }
+        };
+
+        head
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_21() {
+    }
+}