2181

Cipher-vasu · Feb 20, 2022 · b494e3d · b494e3d
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diff --git a/leetcode/2180. Count Integers With Even Digit Sum/README.md b/leetcode/2180. Count Integers With Even Digit Sum/README.md
@@ -36,7 +36,7 @@ The 14 integers less than or equal to 30 whose digit sums are even are
 ## Solution 1. Brute Force
 
 ```cpp
-// OJ: https://leetcode.com/contest/weekly-contest-281/problems/count-integers-with-even-digit-sum/
+// OJ: https://leetcode.com/problems/count-integers-with-even-digit-sum/
 // Author: github.com/lzl124631x
 // Time: O(NlgN)
 // Space: O(1)

diff --git a/leetcode/2181. Merge Nodes in Between Zeros/README.md b/leetcode/2181. Merge Nodes in Between Zeros/README.md
@@ -67,4 +67,74 @@ public:
         return dummy.next;
     }
 };
-```
+```
+
+## Solution 2.
+
+If we are asked to do it in-place.
+
+```cpp
+// OJ: https://leetcode.com/problems/merge-nodes-in-between-zeros/
+// Author: github.com/lzl124631x
+// Time: O(N)
+// Space: O(1) as it's done in-place
+class Solution {
+public:
+    ListNode* mergeNodes(ListNode* head) {
+        ListNode dummy, *tail = &dummy;
+        while (head) {
+            if (head->val == 0) head = head->next;
+            if (!head) break;
+            auto node = head;
+            head = head->next;
+            while (head->val != 0) {
+                node->val += head->val;
+                head = head->next;
+            }
+            tail->next = node;
+            tail = tail->next;
+            node->next = nullptr;
+        }
+        return dummy.next;
+    }
+};
+```
+
+If you are asked to add the code to free node:
+
+```cpp
+// OJ: https://leetcode.com/problems/merge-nodes-in-between-zeros/
+// Author: github.com/lzl124631x
+// Time: O(N)
+// Space: O(1) as it's done in-place
+class Solution {
+public:
+    ListNode* mergeNodes(ListNode* head) {
+        ListNode dummy, *tail = &dummy;
+        while (head) {
+            if (head->val == 0) {
+                auto p = head;
+                head = head->next;
+                delete p;
+            }
+            if (!head) break;
+            auto node = head;
+            head = head->next;
+            while (head->val != 0) {
+                node->val += head->val;
+                auto p = head;
+                head = head->next;
+                delete p;
+            }
+            tail->next = node;
+            tail = tail->next;
+            node->next = nullptr;
+        }
+        return dummy.next;
+    }
+};
+```
+
+## Discuss
+
+https://leetcode.com/problems/merge-nodes-in-between-zeros/discuss/1784739/