feat: update solutions to lc problem: No.0021. Merge Two Sorted Lists

yanglbme · yanglbme · commit 9d4d8ea5e556 · 2021-05-29T23:53:49.000+08:00
diff --git a/solution/0000-0099/0021.Merge Two Sorted Lists/README.md b/solution/0000-0099/0021.Merge Two Sorted Lists/README.md
@@ -46,6 +46,8 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
+迭代遍历两链表，比较节点值 val 的大小，进行节点串联，得到最终链表。
+
 <!-- tabs:start -->
 
 ### **Python3**
@@ -125,7 +127,7 @@ class Solution {
 class Solution {
 public:
     ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
-        ListNode* dummy = new ListNode(0);
+        ListNode* dummy = new ListNode();
         ListNode* cur = dummy;
         while (l1 && l2) {
             if (l1->val <= l2->val) {
@@ -137,11 +139,7 @@ public:
             }
             cur = cur->next;
         }
-        if (l1) {
-            cur->next = l1;
-        } else if (l2) {
-            cur->next = l2;
-        }
+        cur->next = l1 ? l1 : l2;
         return dummy->next;
     }
 };
@@ -162,21 +160,21 @@ public:
  * @param {ListNode} l2
  * @return {ListNode}
  */
-var mergeTwoLists = function (l1, l2) {
-  const dummy = new ListNode(0);
-  let cur = dummy;
-  while (l1 && l2) {
-    if (l1.val <= l2.val) {
-      cur.next = l1;
-      l1 = l1.next;
-    } else {
-      cur.next = l2;
-      l2 = l2.next;
+var mergeTwoLists = function(l1, l2) {
+    const dummy = new ListNode();
+    let cur = dummy;
+    while (l1 && l2) {
+        if (l1.val <= l2.val) {
+            cur.next = l1;
+            l1 = l1.next;
+        } else {
+            cur.next = l2;
+            l2 = l2.next;
+        }
+        cur = cur.next;
     }
-    cur = cur.next;
-  }
-  cur.next = l1 || l2;
-  return dummy.next;
+    cur.next = l1 || l2;
+    return dummy.next;
 };
 ```
 
@@ -212,6 +210,38 @@ func mergeTwoLists(l1 *ListNode, l2 *ListNode) *ListNode {
 }
 ```
 
+### **Ruby**
+
+```rb
+# Definition for singly-linked list.
+# class ListNode
+#     attr_accessor :val, :next
+#     def initialize(val = 0, _next = nil)
+#         @val = val
+#         @next = _next
+#     end
+# end
+# @param {ListNode} l1
+# @param {ListNode} l2
+# @return {ListNode}
+def merge_two_lists(l1, l2)
+    dummy = ListNode.new()
+    cur = dummy
+    while l1 && l2
+        if l1.val <= l2.val
+            cur.next = l1
+            l1 = l1.next
+        else
+            cur.next = l2
+            l2 = l2.next
+        end
+        cur = cur.next
+    end
+    cur.next = l1 || l2
+    dummy.next
+end
+```
+
 ### **...**
 
 ```
diff --git a/solution/0000-0099/0021.Merge Two Sorted Lists/README_EN.md b/solution/0000-0099/0021.Merge Two Sorted Lists/README_EN.md
@@ -115,7 +115,7 @@ class Solution {
 class Solution {
 public:
     ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
-        ListNode* dummy = new ListNode(0);
+        ListNode* dummy = new ListNode();
         ListNode* cur = dummy;
         while (l1 && l2) {
             if (l1->val <= l2->val) {
@@ -127,11 +127,7 @@ public:
             }
             cur = cur->next;
         }
-        if (l1) {
-            cur->next = l1;
-        } else if (l2) {
-            cur->next = l2;
-        }
+        cur->next = l1 ? l1 : l2;
         return dummy->next;
     }
 };
@@ -152,21 +148,21 @@ public:
  * @param {ListNode} l2
  * @return {ListNode}
  */
-var mergeTwoLists = function (l1, l2) {
-  const dummy = new ListNode(0);
-  let cur = dummy;
-  while (l1 && l2) {
-    if (l1.val <= l2.val) {
-      cur.next = l1;
-      l1 = l1.next;
-    } else {
-      cur.next = l2;
-      l2 = l2.next;
+var mergeTwoLists = function(l1, l2) {
+    const dummy = new ListNode();
+    let cur = dummy;
+    while (l1 && l2) {
+        if (l1.val <= l2.val) {
+            cur.next = l1;
+            l1 = l1.next;
+        } else {
+            cur.next = l2;
+            l2 = l2.next;
+        }
+        cur = cur.next;
     }
-    cur = cur.next;
-  }
-  cur.next = l1 || l2;
-  return dummy.next;
+    cur.next = l1 || l2;
+    return dummy.next;
 };
 ```
 
@@ -202,6 +198,38 @@ func mergeTwoLists(l1 *ListNode, l2 *ListNode) *ListNode {
 }
 ```
 
+### **Ruby**
+
+```rb
+# Definition for singly-linked list.
+# class ListNode
+#     attr_accessor :val, :next
+#     def initialize(val = 0, _next = nil)
+#         @val = val
+#         @next = _next
+#     end
+# end
+# @param {ListNode} l1
+# @param {ListNode} l2
+# @return {ListNode}
+def merge_two_lists(l1, l2)
+    dummy = ListNode.new()
+    cur = dummy
+    while l1 && l2
+        if l1.val <= l2.val
+            cur.next = l1
+            l1 = l1.next
+        else
+            cur.next = l2
+            l2 = l2.next
+        end
+        cur = cur.next
+    end
+    cur.next = l1 || l2
+    dummy.next
+end
+```
+
 ### **...**
 
 ```
diff --git a/solution/0000-0099/0021.Merge Two Sorted Lists/Solution.cpp b/solution/0000-0099/0021.Merge Two Sorted Lists/Solution.cpp
@@ -11,7 +11,7 @@
 class Solution {
 public:
     ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
-        ListNode* dummy = new ListNode(0);
+        ListNode* dummy = new ListNode();
         ListNode* cur = dummy;
         while (l1 && l2) {
             if (l1->val <= l2->val) {
@@ -23,11 +23,7 @@ class Solution {
             }
             cur = cur->next;
         }
-        if (l1) {
-            cur->next = l1;
-        } else if (l2) {
-            cur->next = l2;
-        }
+        cur->next = l1 ? l1 : l2;
         return dummy->next;
     }
 };
diff --git a/solution/0000-0099/0021.Merge Two Sorted Lists/Solution.js b/solution/0000-0099/0021.Merge Two Sorted Lists/Solution.js
@@ -10,19 +10,19 @@
  * @param {ListNode} l2
  * @return {ListNode}
  */
-var mergeTwoLists = function (l1, l2) {
-  const dummy = new ListNode(0);
+ var mergeTwoLists = function(l1, l2) {
+  const dummy = new ListNode();
   let cur = dummy;
   while (l1 && l2) {
-    if (l1.val <= l2.val) {
-      cur.next = l1;
-      l1 = l1.next;
-    } else {
-      cur.next = l2;
-      l2 = l2.next;
-    }
-    cur = cur.next;
+      if (l1.val <= l2.val) {
+          cur.next = l1;
+          l1 = l1.next;
+      } else {
+          cur.next = l2;
+          l2 = l2.next;
+      }
+      cur = cur.next;
   }
   cur.next = l1 || l2;
   return dummy.next;
-};
+};
diff --git a/solution/0000-0099/0021.Merge Two Sorted Lists/Solution.rb b/solution/0000-0099/0021.Merge Two Sorted Lists/Solution.rb
@@ -1,25 +1,27 @@
 # Definition for singly-linked list.
 # class ListNode
 #     attr_accessor :val, :next
-#     def initialize(val)
+#     def initialize(val = 0, _next = nil)
 #         @val = val
-#         @next = nil
+#         @next = _next
 #     end
 # end
-
 # @param {ListNode} l1
 # @param {ListNode} l2
 # @return {ListNode}
 def merge_two_lists(l1, l2)
-  if l1.nil?
-    l2
-  elsif l2.nil?
-    l1
-  elsif l1.val < l2.val
-    l1.next = merge_two_lists(l1.next, l2)
-    l1
-  else
-    l2.next = merge_two_lists(l1, l2.next)
-    l2
+  dummy = ListNode.new()
+  cur = dummy
+  while l1 && l2
+      if l1.val <= l2.val
+          cur.next = l1
+          l1 = l1.next
+      else
+          cur.next = l2
+          l2 = l2.next
+      end
+      cur = cur.next
   end
-end
+  cur.next = l1 || l2
+  dummy.next
+end
