feat: add c solution to lc problem: No.0002 (#4426)

Author: pranjal030404

solution/0000-0099/0002.Add Two Numbers/README.md

@@ -494,6 +494,52 @@ proc addTwoNumbers(l1: var SinglyLinkedList, l2: var SinglyLinkedList): SinglyLi
   result = aggregate
 ```
 
+#### C
+
+```c
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     struct ListNode *next;
+ * };
+ */
+
+struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
+    struct ListNode* dummy = (struct ListNode*) malloc(sizeof(struct ListNode));
+    dummy->val = 0;
+    dummy->next = NULL;
+    struct ListNode* curr = dummy;
+    int carry = 0;
+
+    while (l1 != NULL || l2 != NULL || carry != 0) {
+        int sum = carry;
+        if (l1 != NULL) {
+            sum += l1->val;
+            l1 = l1->next;
+        }
+        if (l2 != NULL) {
+            sum += l2->val;
+            l2 = l2->next;
+        }
+
+        carry = sum / 10;
+        int val = sum % 10;
+
+        struct ListNode* newNode = (struct ListNode*) malloc(sizeof(struct ListNode));
+        newNode->val = val;
+        newNode->next = NULL;
+        curr->next = newNode;
+        curr = curr->next;
+    }
+
+    struct ListNode* result = dummy->next;
+    free(dummy);
+    return result;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0000-0099/0002.Add Two Numbers/README_EN.md

@@ -490,6 +490,52 @@ proc addTwoNumbers(l1: var SinglyLinkedList, l2: var SinglyLinkedList): SinglyLi
   result = aggregate
 ```
 
+#### C
+
+```c
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     struct ListNode *next;
+ * };
+ */
+
+struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
+    struct ListNode* dummy = (struct ListNode*) malloc(sizeof(struct ListNode));
+    dummy->val = 0;
+    dummy->next = NULL;
+    struct ListNode* curr = dummy;
+    int carry = 0;
+
+    while (l1 != NULL || l2 != NULL || carry != 0) {
+        int sum = carry;
+        if (l1 != NULL) {
+            sum += l1->val;
+            l1 = l1->next;
+        }
+        if (l2 != NULL) {
+            sum += l2->val;
+            l2 = l2->next;
+        }
+
+        carry = sum / 10;
+        int val = sum % 10;
+
+        struct ListNode* newNode = (struct ListNode*) malloc(sizeof(struct ListNode));
+        newNode->val = val;
+        newNode->next = NULL;
+        curr->next = newNode;
+        curr = curr->next;
+    }
+
+    struct ListNode* result = dummy->next;
+    free(dummy);
+    return result;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0000-0099/0002.Add Two Numbers/Solution.c

@@ -0,0 +1,41 @@
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     struct ListNode *next;
+ * };
+ */
+
+struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
+    struct ListNode* dummy = (struct ListNode*) malloc(sizeof(struct ListNode));
+    dummy->val = 0;
+    dummy->next = NULL;
+    struct ListNode* curr = dummy;
+    int carry = 0;
+
+    while (l1 != NULL || l2 != NULL || carry != 0) {
+        int sum = carry;
+        if (l1 != NULL) {
+            sum += l1->val;
+            l1 = l1->next;
+        }
+        if (l2 != NULL) {
+            sum += l2->val;
+            l2 = l2->next;
+        }
+
+        carry = sum / 10;
+        int val = sum % 10;
+
+        struct ListNode* newNode = (struct ListNode*) malloc(sizeof(struct ListNode));
+        newNode->val = val;
+        newNode->next = NULL;
+        curr->next = newNode;
+        curr = curr->next;
+    }
+
+    struct ListNode* result = dummy->next;
+    free(dummy);
+    return result;
+}