PAT A 1052 Linked List Sorting

A linked list consists of a series of structures, which are not nec‐essarily adjacent in memory. We assume that each structure con‐tains an integer key and a Next pointer to the next structure. Now given a linked list, you are supposed to sort the structures according to their key values in increasing order.
Input Specification:
Each input file contains one test case. For each case, the first line contains a positive () and an address of the head node, where is the total number of nodes in memory and the ad‐dress of a node is a 5-digit positive integer. NULL is represented by .
Then lines follow, each describes a node in the format:
Address Key Next
where Address is the address of the node in memory, Key is an in‐teger in [], and Next is the address of the next node. It is guaranteed that all the keys are distinct and there is no cycle in the linked list starting from the head node.
Output Specification:
For each test case, the output format is the same as that of the input, where is the total number of nodes in the list and all the nodes must be sorted order.
Sample Input:
5 00001
11111 100 -1
00001 0 22222
33333 100000 11111
12345 -1 33333
22222 1000 12345
Sample Output:
5 12345
12345 -1 00001
00001 0 11111
11111 100 22222
22222 1000 33333
33333 100000 -1

#include <iostream>
#include <algorithm>
#include <cstring>using namespace std;int n,head;
const int N = 1e5+10;
struct Node
{int add;int data;int next;bool flag;bool exist;//为了防止全部无效的情况bool operator <(const Node &t) const{if(flag != t.flag) return flag > t.flag;else return data < t.data;}
}node[N];int main()
{cin>>n>>head;int add = 0,next = 0,data = 0;for(int i=0;i<n;i++){cin>>add>>data>>next;node[add].add = add;node[add].next = next;node[add].data = data;node[add].exist = true;//至少是个节点}int cnt = 0;for(int i=head;i!=-1;i=node[i].next){if(node[i].exist == true)//为了杜绝头指针无next{node[i].flag = true;cnt++;}else break;}sort(node,node+N);if(cnt == 0) cout<<"0 -1"<<endl;//没有节点在链上else{cout<<cnt<<' ';printf("%05d\n",node[0].add);for(int i=0;i<cnt;i++){if(i<cnt-1){printf("%05d %d %05d\n",node[i].add,node[i].data,node[i+1].add);}else{printf("%05d %d ",node[i].add,node[i].data);printf("-1\n");}}}return 0;
}