Reversing Linked List

Given a constant K and a singly linked list L, you are supposed to reverse the links of every K elements on L. For example, given L being 1→2→3→4→5→6, if K=3, then you must output 3→2→1→6→5→4; if K=4, you must output 4→3→2→1→5→6.

Input Specification:

Each input file contains one test case. For each case, the first line contains the address of the first node, a positive N (≤105) which is the total number of nodes, and a positive K (≤N) which is the length of the sublist to be reversed. The address of a node is a 5-digit nonnegative integer, and NULL is represented by -1.

Then N lines follow, each describes a node in the format:

Address Data Next

where Address is the position of the node, Data is an integer, and Next is the position of the next node.

Output Specification:

For each case, output the resulting ordered linked list. Each node occupies a line, and is printed in the same format as in the input.

Sample Input:

00100 6 4
00000 4 99999
00100 1 12309
68237 6 -1
33218 3 00000
99999 5 68237
12309 2 33218

Sample Output:

00000 4 33218
33218 3 12309
12309 2 00100
00100 1 99999
99999 5 68237
68237 6 -1


做了好久 = = 纪念一下 调bug太长时间了 一开始用链表 有个超时 用数据就快了 牺牲空间换时间。。。。

#include <stdio.h>

#define MaxSize 100001

struct Node{
    int data;
    int next;
    int pre;
};
typedef struct Node Node;

void Read(int n,Node* List);
void Print(int firstnode,Node* List);
void reverse(Node* List,int k,int firstnode);
void Addpre(Node* List, int firstnode);
void reversePrint(Node* List,int firstnode);
int calculateTail(int head,Node* List,int k); // 给出头 计算包括头的第k个元素 即连续k个元素的尾部下标

int main(){
    Node List[MaxSize];
    int firstnode,n,k;
    scanf("%d %d %d",&firstnode,&n,&k);
    Read(n, List);
 //   Print(firstnode, List);
    Addpre(List, firstnode);
 //   reversePrint(List,firstnode);
    reverse(List, k, firstnode);
    return 0;
}

void Read(int n,Node* List){
    int a;
    while (n) {
        scanf("%d",&a);
        scanf("%d %d",&List[a].data,&List[a].next);
        a = List[a].next;
        --n;
    }
}

void Print(int firstnode,Node* List){
    int a = firstnode;
    while (a != -1) {
        if(List[a].next != -1){
            printf("%05d %d %05d\n",a,List[a].data,List[a].next);
        }else{
            printf("%05d %d %d",a,List[a].data,List[a].next);
        }
        a = List[a].next;
    }
}

void reverse(Node* List,int k,int firstnode){
    int head, tail, a;
    int i = k;
    head = firstnode;
    tail = calculateTail(head, List, k);
//    printf("%d\n",List[tail].data);
    while (tail != -1) {
        head = List[tail].next;
//        printf("head is %d\n",head);
        a = tail;
        while (i) {
            if(i == 1 && head == -1){
//                printf("flag = 0\n");
                printf("%05d %d %d",a,List[a].data,head);
                return;
            }else if(i == 1 && calculateTail(head, List, k) != -1){
    //            printf("flag = 1\n");
                printf("%05d %d %05d\n",a,List[a].data,calculateTail(head, List, k));
            }else if(i == 1 && calculateTail(head, List, k) == -1){
                printf("%05d %d %05d\n",a,List[a].data,head);
            }else{
//                printf("flag = 2\n");
                printf("%05d %d %05d\n",a,List[a].data,List[a].pre);
            }
            a = List[a].pre;
            --i;
        }
        tail = calculateTail(head, List, k);
 //       printf("tail is %d\n",tail);
        i = k;
    }
    a = head;
    while (List[a].next != -1) {
   //     printf("flag = 3\n");
        printf("%05d %d %05d\n",a,List[a].data,List[a].next);
        a = List[a].next;
    }
    printf("%05d %d %d",a,List[a].data,List[a].next);
}

void Addpre(Node* List, int firstnode){
    int a = firstnode;
    int t = a;
    List[a].pre = -1;
    a = List[a].next;
    while (a != -1) {
        List[a].pre = t;
        t = a;
        a = List[a].next;
    }
}

void reversePrint(Node* List,int firstnode){
    int a = firstnode;
    while (List[a].next != -1) {
        a = List[a].next;
    }
    while (List[a].pre != -1) {
        printf("%05d %d %05d\n",a,List[a].data,List[a].pre);
        a = List[a].pre;
    }
    printf("%05d %d %d",a,List[a].data,List[a].pre);
}

int calculateTail(int head,Node* List,int k){
    int a = head;
    int i = k - 1;
    while (i && a != -1) {
        a = List[a].next;
        --i;
    }
    return a;
}