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  • 《Cracking the Coding Interview》——第2章:链表——题目2

    2014-03-18 02:24

    题目:给定一个单链表,找出倒数第K个节点。

    解法:让一个指针先走K步,然后俩指针一起走到尽头。当然也可以先走到尽头数出链表的长度,然后第二次少走K步。其实耗费的工夫是一样的,但貌似总有人觉得第一种方法很巧妙很优美。

    代码:

     1 // 2.2 Remove a node from middle of a linked list
     2 #include <cstdio>
     3 using namespace std;
     4 
     5 struct ListNode {
     6     int val;
     7     struct ListNode *next;
     8     ListNode(int x): val(x), next(nullptr) {};
     9 };
    10 
    11 class Solution {
    12 public:
    13     ListNode* findKthNode(ListNode *head, int k) {
    14         if (head == nullptr || k < 1) {
    15             return head;
    16         }
    17         struct ListNode *p1, *p2;
    18         
    19         p1 = p2 = head;
    20         int i;
    21         for (i = 0; i < k; ++i) {
    22             p2 = p2->next;
    23             if (p2 == nullptr) {
    24                 return head;
    25             }
    26         }
    27         while (p2 != nullptr) {
    28             p1 = p1->next;
    29             p2 = p2->next;
    30         }
    31         
    32         return p1;
    33     }
    34 };
    35 
    36 int main()
    37 {
    38     int i;
    39     int n, k;
    40     int val;
    41     struct ListNode *head, *ptr;
    42     Solution sol;
    43     
    44     while (scanf("%d", &n) == 1 && n > 0) {
    45         // create a linked list
    46         ptr = head = nullptr;
    47         for (i = 0; i < n; ++i) {
    48             scanf("%d", &val);
    49             if (head == nullptr) {
    50                 head = ptr = new ListNode(val);
    51             } else {
    52                 ptr->next = new ListNode(val);
    53                 ptr = ptr->next;
    54             }
    55         }
    56         
    57         // find the kth node from the end of the list
    58         scanf("%d", &k);
    59         ptr = sol.findKthNode(head, k);
    60         printf("%d
    ", ptr->val);
    61         
    62         /*
    63         // print the list
    64         printf("%d", head->val);
    65         ptr = head->next;
    66         while (ptr != nullptr) {
    67             printf("->%d", ptr->val);
    68             ptr = ptr->next;
    69         }
    70         printf("
    ");
    71         */
    72         
    73         // delete the list
    74         while (head != nullptr) {
    75             ptr = head->next;
    76             delete head;
    77             head = ptr;
    78         }
    79     }
    80     
    81     return 0;
    82 }
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  • 原文地址:https://www.cnblogs.com/zhuli19901106/p/3606687.html
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