init commit

archive/algorithm/leetcode/19.c

@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include <malloc.h>
+#include <math.h>
+
+// 删除链表的倒数第N个节点
+// https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/
+
+// 更优解:双指针
+struct ListNode
+{
+    int val;
+    struct ListNode *next;
+};
+
+struct ListNode *removeNthFromEnd(struct ListNode *head, int n)
+{
+    if (head->next == NULL)
+    {
+        return NULL;
+    }
+    int pos = 0, len = n + 1;
+    struct ListNode **arr = malloc(sizeof(struct ListNode *) * len);
+    struct ListNode *temp = malloc(sizeof(struct ListNode));
+    temp->next = head;
+    head = temp;
+    while (temp != NULL)
+    {
+        arr[pos % len] = temp;
+        pos++;
+        temp = temp->next;
+    }
+    pos = abs((pos - len) % len);
+    if (arr[pos]->next == NULL)
+    {
+        arr[abs((pos - 1) % len)]->next = NULL;
+    }
+    else
+    {
+        arr[pos]->next = arr[pos]->next->next;
+    }
+
+    return head->next;
+}
+
+int main()
+{
+    struct ListNode *head = malloc(sizeof(struct ListNode)), *next = malloc(sizeof(struct ListNode)), *tmp;
+    head->val = 1;
+    head->next = next;
+
+    next->val = 2;
+    next->next = malloc(sizeof(struct ListNode));
+    next = next->next;
+
+    next->val = 3;
+    next->next = malloc(sizeof(struct ListNode));
+    next = next->next;
+    next->val = 4;
+    next->next = malloc(sizeof(struct ListNode));
+    next = next->next;
+    next->val = 5;
+    next->next = NULL;
+
+    removeNthFromEnd(head, 1);
+    return 0;
+}