LeetCode OJ Reverse Linked List

题目

思路
翻转单向链表，这里题目要求用递归和非递归实现，具体思路见代码。

代码
a）非递归

struct ListNode* reverseList(struct ListNode* head) {    struct ListNode * Before = NULL;    struct ListNode * OriPresent = head;    while (OriPresent != NULL) {        struct ListNode * Present = (struct ListNode*)malloc(sizeof(struct ListNode));        Present->val = OriPresent->val;        Present->next = Before;        Before = Present;        OriPresent = OriPresent->next;    }    return Before;}

b）递归

struct ListNode * reverse(struct ListNode * Before, struct ListNode * OriPresent) {    if (OriPresent == NULL) return Before;    struct ListNode * Present = (struct ListNode*)malloc(sizeof(struct ListNode));    Present->next = Before;    Present->val = OriPresent->val;    return reverse(Present, OriPresent->next);}struct ListNode* reverseList(struct ListNode* head) {    return reverse(NULL, head);}