A1097. Deduplication on a Linked List

Given a singly linked list L with integer keys, you are supposed to remove the nodes with duplicated absolute values of the keys. That is, for each value K, only the first node of which the value or absolute value of its key equals K will be kept. At the mean time, all the removed nodes must be kept in a separate list. For example, given L being 21→-15→-15→-7→15, you must output 21→-15→-7, and the removed list -15→15.

Input Specification:

Each input file contains one test case. For each case, the first line contains the address of the first node, and a positive N (<= 10⁵) which is the total number of nodes. 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 Key Next

where Address is the position of the node, Key is an integer of which absolute value is no more than 10⁴, and Next is the position of the next node.

Output Specification:

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

Sample Input:

00100 5
99999 -7 87654
23854 -15 00000
87654 15 -1
00000 -15 99999
00100 21 23854

Sample Output:

00100 21 23854
23854 -15 99999
99999 -7 -1
00000 -15 87654
87654 15 -1

 #include<cstdio>
 #include<iostream>
 #include<algorithm>
 #include<map>
 using namespace std;
 typedef struct NODE{
     int lt, rt;
     int data;
     int rank;
     int valid;
     NODE(){
         valid = -;  //分为3类。不重复的合法数据为1，重复的合法数据为0，非法数据为-1
     }
 }node;
 node nds[];
 map<int, int> mp;
 bool cmp(node a, node b){
     if(a.valid != b.valid)
         return a.valid > b.valid;
     else return a.rank < b.rank;
 }
 int main(){
     int N, head;
     scanf("%d%d", &head, &N);
     int addr;
     for(int i = ; i < N; i++){
         scanf("%d", &addr);
         nds[addr].lt = addr;
         scanf("%d %d", &nds[addr].data, &nds[addr].rt);
     }
     int pt = head, index = ;
     while(pt != -){
         if(mp.count(abs(nds[pt].data)) == ){
             mp[abs(nds[pt].data)] = ;
             nds[pt].valid = ;
         }else{
             nds[pt].valid = ;
         }
         nds[pt].rank = index++;
         pt = nds[pt].rt;
     }
     sort(nds, nds + , cmp);
     int dele = -;
     for(int i = ; i < index; i++){
         if(nds[i].valid != ){
             dele = i;
             break;
         }
     }
     if(dele == -)
         dele = ;
     for(int i = ; i < dele; i++){
         if(i < dele - )
             printf("%05d %d %05d\n", nds[i].lt, nds[i].data, nds[i + ].lt);
         else printf("%05d %d -1\n", nds[i].lt, nds[i].data);
     }
     for(int i = dele; i < index; i++){
         if(i < index - )
             printf("%05d %d %05d\n", nds[i].lt, nds[i].data, nds[i + ].lt);
         else printf("%05d %d -1\n", nds[i].lt, nds[i].data);
     }
     cin >> N;
     return ;
 }

总结：

1、在遍历合法链表时给每个节点编号，之后按照编号进行排序，既可保持链表顺序，又方便输出。

2、给链表节点打不同的标记，再利用排序sort的分类的特点，可以对链表的节点进行分类。

3、利用 map 来记录某个节点的data是否在之前存在过。