【PAT】A1121 Damn Single【散列】

“Damn Single (单身狗)” is the Chinese nickname for someone who is being single. You are supposed to find those who are alone in a big party, so they can be taken care of.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (≤ 50,000), the total number of couples. Then N lines of the couples follow, each gives a couple of ID’s which are 5-digit numbers (i.e. from 00000 to 99999). After the list of couples, there is a positive integer M (≤ 10,000) followed by M ID’s of the party guests. The numbers are separated by spaces. It is guaranteed that nobody is having bigamous marriage (重婚) or dangling with more than one companion.

Output Specification:

First print in a line the total number of lonely guests. Then in the next line, print their ID’s in increasing order. The numbers must be separated by exactly 1 space, and there must be no extra space at the end of the line.

Sample Input:

3
11111 22222
33333 44444
55555 66666
7
55555 44444 10000 88888 22222 11111 23333

Sample Output:

5
10000 23333 44444 55555 88888

题意

给出若干对夫妻以及一个party上的所有成员，求party中所有的单身狗（一对夫妻只来了一个也属于单身），要求按ID从小到大输出。

思路

简单模拟即可。用couple[i] = j表示i的配偶是j（如果i是单身，则j为-1）。具体逻辑看代码注释。

代码

#include <cstdio>
#include <algorithm>
#define MAX_ID 1000000
#define MAX_M 10000
using namespace std;