Remove Nth node from end of list

Signed-off-by: begeekmyfriend <[email protected]>

019_remove_nth_node_from_end_of_list/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test remove_end.c

019_remove_nth_node_from_end_of_list/remove_end.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+ struct ListNode {
+     int val;
+     struct ListNode *next;
+ };
+
+struct ListNode* removeNthFromEnd(struct ListNode* head, int n) {
+    struct ListNode *p, *prev, dummy;
+    if (n < 1) return NULL;
+
+    dummy.next = head;
+    p = prev = &dummy;
+    while (n-- > 0) {
+        p = p->next;
+    }
+
+    while (p->next != NULL) {
+        p = p->next;
+        prev = prev->next;
+    }
+
+    struct ListNode *tmp = prev->next;
+    prev->next = tmp->next;
+    if (tmp == head) {
+        head = tmp->next;
+    }
+    free(tmp);
+    return head;
+}
+
+int main(int argc, char **argv)
+{
+    int i;
+    struct ListNode *list, *p, *prev = NULL;
+    for (i = 1; i < argc; i++) {
+        p = malloc(sizeof(*p));
+        p->val = atoi(argv[i]);
+        p->next = NULL;
+        if (i == 1) {
+            list = p;
+        }
+        if (prev != NULL) {
+            prev->next = p;
+        }
+        prev = p;
+    }
+
+    list = removeNthFromEnd(list, 1);
+    if (list != NULL) {
+        for (p = list; p != NULL; p = p->next) {
+            printf("%d\n", p->val);
+        }
+    }
+
+    return 0;
+}