Time: 157 ms (92.91%), Space: 120.7 MB (87.76%) - LeetHub

Author: MishkatIT

2816-double-a-number-represented-as-a-linked-list/2816-double-a-number-represented-as-a-linked-list.cpp

@@ -0,0 +1,57 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* reverse(ListNode* head) {
+        ListNode* curr_node = head;
+        ListNode* next_node = curr_node->next;
+        curr_node->next = nullptr;
+
+        while (next_node != nullptr) {
+            ListNode* next_next_node = next_node->next;
+            next_node->next = curr_node;
+
+            curr_node = next_node;
+            next_node = next_next_node;
+        }
+
+        return curr_node;
+    }
+
+    ListNode* lesgoo(ListNode* head) {
+        ListNode* new_head = new ListNode(-1);
+        new_head->next = head;
+        ListNode* curr_node = new_head;
+        int carry = 0;
+
+        while (curr_node->next != nullptr) {
+            curr_node->next->val += curr_node->next->val;
+            curr_node->next->val += carry;
+            carry = curr_node->next->val / 10;
+            curr_node->next->val %= 10;
+
+            curr_node = curr_node->next;
+        }
+
+        while (carry > 0) {
+            curr_node->next = new ListNode(carry % 10);
+            carry /= 10;
+            curr_node = curr_node->next;
+        }
+
+        return new_head->next;
+    }
+
+    ListNode* doubleIt(ListNode* head) {
+        ListNode* headdd = reverse(head);
+        return reverse(lesgoo(headdd));
+    }
+};