"Remove Duplicates from Sorted List II"

Author: lennylxx

README.md

@@ -218,7 +218,7 @@ The `☢` means that you need to have a LeetCode Premium Subscription.
 | 85  | [Maximal Rectangle]                                          |                    |
 | 84  | [Largest Rectangle in Histogram]                             |                    |
 | 83  | [Remove Duplicates from Sorted List]                         | [C](src/83.c)      |
-| 82  | [Remove Duplicates from Sorted List II]                      |                    |
+| 82  | [Remove Duplicates from Sorted List II]                      | [C](src/82.c)      |
 | 81  | [Search in Rotated Sorted Array II]                          | [C](src/81.c)      |
 | 80  | [Remove Duplicates from Sorted Array II]                     | [C](src/80.c)      |
 | 79  | [Word Search]                                                | [C](src/79.c)      |

src/82.c

@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct ListNode {
+    int val;
+    struct ListNode *next;
+};
+
+struct ListNode* deleteDuplicates(struct ListNode* head) {
+    if (head == NULL || head->next == NULL) return head;
+
+    struct ListNode *dummy = malloc(sizeof(struct ListNode));
+    dummy->val = 0;
+    dummy->next = head;
+    struct ListNode *pre = dummy;
+    struct ListNode *p = dummy->next;
+    struct ListNode *q = dummy->next->next;
+
+    while (p && q) {
+        if (p->val == q->val) {
+            pre->next = q->next;
+            p = p->next;
+            q = q->next;
+        }
+        else {
+            if (pre->next == q) {
+                p = p->next;
+                q = q->next;
+            }
+            else {
+                pre = pre->next;
+                p = p->next;
+                q = q->next;
+            }
+        }
+    }
+
+    struct ListNode *new_head = dummy->next;
+    free(dummy);
+
+    return new_head;
+}
+
+struct ListNode * buildList(int *nums, int numsSize) {
+    if (numsSize == 0) return NULL;
+
+    struct ListNode *dummy = malloc(sizeof(struct ListNode));
+    dummy->val = 0;
+    struct ListNode *p = dummy;
+    for (int i = 0; i < numsSize; i++) {
+        p->next = malloc(sizeof(struct ListNode));
+        p->next->val = nums[i];
+        p = p->next;
+    }
+    p->next = NULL;
+
+    p = dummy->next;
+    free(dummy);
+
+    return p;
+}
+
+int main() {
+
+    int nums[] = { 1, 2, 2, 2, 3, 3 };
+    struct ListNode *head = buildList(nums, sizeof(nums) / sizeof(nums[0]));
+    struct ListNode *p = head;
+    while (p) {
+        printf("%d->", p->val);
+        p = p->next;
+    }
+    printf("NIL\n");
+
+    struct ListNode *new_head = deleteDuplicates(head);
+
+    p = new_head;
+    while (p) {
+        printf("%d->", p->val);
+        p = p->next;
+    }
+    printf("NIL\n");
+
+    return 0;
+}