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PAT/PATBasic/1065.c
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/**
* 1065. 单身狗(25)
*
* “单身狗”是中文对于单身人士的一种爱称。本题请你从上万人的大型派对中找出落单的客人,
* 以便给予特殊关爱。
*
* 输入格式:
*
* 输入第一行给出一个正整数N(<=50000),是已知夫妻/伴侣的对数;随后N行,每行给出一
* 对夫妻/伴侣——为方便起见,每人对应一个ID号,为5位数字(从00000到99999),ID间以空
* 格分隔;之后给出一个正整数M(<=10000),为参加派对的总人数;随后一行给出这M位客人
* 的ID,以空格分隔。题目保证无人重婚或脚踩两条船。
*
* 输出格式:
*
* 首先第一行输出落单客人的总人数;随后第二行按ID递增顺序列出落单的客人。ID间用1个
* 空格分隔,行的首尾不得有多余空格。
*
* 输入样例:
* 3
* 11111 22222
* 33333 44444
* 55555 66666
* 7
* 55555 44444 10000 88888 22222 11111 23333
* 输出样例:
* 5
* 10000 23333 44444 55555 88888
*/
#include <stdio.h>
int main()
{
int couple[100001] = {0}, N, ID1, ID2, M, count = 0;
/* every pair of 'index' and 'value' are a couple.
* record ID + 1 to avoid '00000' conflict with 0 */
scanf("%d", &N);
for(int i = 0; i < N; i++)
{
scanf("%d %d", &ID1, &ID2); ID1++; ID2++;
couple[ID1] = ID2;
couple[ID2] = ID1;
}
/* Record those who come. If one has a mate then set 0 (means signed in),
* else (means not even in the 'couple-list') set -1 (means bachelor) */
scanf("%d", &M);
for(int i = 0; i < M; i++)
{
scanf("%d", &ID1); ID1++;
if(couple[ID1]) couple[ID1] = 0;
else {couple[ID1] = -1; count++;}
}
/* If couple[ID] is positive but couple[couple[ID]] is zero,
* it means 'ID' didn't come but his/her mate did(signed in). */
for(int i = 0; i < 100001; i++) if(couple[i] > 0 && !couple[couple[i]])
{
couple[couple[i]] = -1;
count++;
}
/* Those whose value is -1 is a bachelor or came alone */
printf("%d\n", count);
for(int i = 0; i < 100001; i++) if(couple[i] == -1)
printf("%05d%c", i - 1, --count ? ' ' : '\0');
return 0;
}