1052 Linked List Sorting （25 分)

2019-03-28

1052 Linked List Sorting （25 分)

A linked list consists of a series of structures, which are not necessarily adjacent in memory. We assume that each structure contains an integer keyand 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 N (<105) and an address of the head node, where N is the total number of nodes in memory and the address of a node is a 5-digit positive integer. NULL is represented by −1.

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

1	Address Key Next

where Address is the address of the node in memory, Key is an integer in [−105,105], 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 N 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

作者: CHEN, Yue

单位: 浙江大学

时间限制: 400 ms

内存限制: 64 MB

代码长度限制: 16 KB

题目大意

给出一个链表，要求对链表进行排序

分析

这题主要坑在于有些点不在链表中。因此用一个map<int,node>存放所有的结点，key为addr。然后从头结点开始，遍历，找出链表中的结点加入vector<node>。然后只需调用sort函数排序即可。

注意处理head为-1的情况，直接输出”0 -1”，否则会有一个测试点段错误。

代码

#include <iostream>
#include <vector>
#include <algorithm>
#include <deque>
#include <map>
#include <set>
#include <cstring>
#include <cmath>
#include<sstream>

using namespace std;

struct node {
    int addr;
    int key;
    int next;

    node(int addr, int key, int next) : addr(addr), key(key), next(next) {}

    node() {}
};

bool cmp(node n1, node n2) {
    return n1.key < n2.key;
}

map<int, node> linklist;
vector<node> sorted;

int main() {
    int n, head;
    int addr, key, next;
    cin >> n >> head;
    for (int i = 0; i < n; i++) {
        cin >> addr >> key >> next;
        node nod(addr, key, next);
        linklist[addr] = nod;
    }

    while (head != -1) {
        sorted.push_back(linklist[head]);
        head = linklist[head].next;
    }
    if (sorted.size() == 0) {
        cout << "0 -1" << endl;
        return 0;
    }
    sort(sorted.begin(), sorted.end(), cmp);

    printf("%d %05d\n", sorted.size(), sorted[0].addr);
    int i;
    for (i = 0; i < sorted.size() - 1; i++) {
        printf("%05d %d %05d\n", sorted[i].addr, sorted[i].key, sorted[i + 1].addr);
    }
    printf("%05d %d -1\n", sorted[i].addr, sorted[i].key);
    return 0;
}