The LeetCode problem [21]'s solution.

Author: hypeagle

src/21.c

@@ -0,0 +1,71 @@
+#include <stdio.h>
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ * int val;
+ * struct ListNode *next;
+ * };
+ */
+struct ListNode {
+ int val;
+ struct ListNode *next;
+};
+
+struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2) {
+ struct ListNode *retList = NULL, *indexList = NULL;
+ struct ListNode *first = l1, *two = l2;
+
+ if(first == NULL) {
+ return two;
+ } else if(two == NULL) {
+ return first;
+ } else if(first->val > two->val) {
+ retList = two;
+ two = two->next;
+
+ retList->next = NULL;
+ indexList = retList;
+ } else {
+ retList = first;
+ first = first->next;
+
+ retList->next = NULL;
+ indexList = retList;
+ }
+
+ while(first || two) {
+ if(first == NULL) {
+ indexList->next = two;
+ two = two->next;
+
+ indexList = indexList->next;
+ indexList->next = NULL;
+ } else if(two == NULL) {
+ indexList->next = first;
+ first = first->next;
+
+ indexList = indexList->next;
+ indexList->next = NULL;
+ } else if(first->val > two->val) {
+ indexList->next = two;
+ two = two->next;
+
+ indexList = indexList->next;
+ indexList->next = NULL;
+ } else {
+ indexList->next = first;
+ first = first->next;
+
+ indexList = indexList->next;
+ indexList->next = NULL;
+ }
+ }
+
+ return retList;
+}
+
+int main()
+{
+ return 0;
+}