Severe acute respiratory syndrome (SARS), an atypical pneumonia of unknown aetiology, was recognized as a global threat in mid-March 2003. To minimize transmission to others, the best strategy is to separate the suspects from others.
In the Not-Spreading-Your-Sickness University (NSYSU), there are many student groups. Students in the same group intercommunicate with each other frequently, and a student may join several groups. To prevent the possible transmissions of SARS, the NSYSU collects the member lists of all student groups, and makes the following rule in their standard operation procedure (SOP).
Once a member in a group is a suspect, all members in the group are suspects.
However, they find that it is not easy to identify all the suspects when a student is recognized as a suspect. Your job is to write a program which finds all the suspects.
For each case, output the number of suspects in one line.
Sample Input
100 4
2 1 2
5 10 13 11 12 14
2 0 1
2 99 2
200 2
1 5
5 1 2 3 4 5
1 0
0 0
Sample Output
4
1
1
问题简述：为防止传染病传播，需将正常人与病人分开，第一行输入n和m（代表学生人数，m代表组数），然后将n个学生从0——n-1编号。接下来的m行输入的第一个数代表学生人数，接着输入学生编号，以0为结束标志。已知0号患病，问需隔离的人数。
问题思路：用并查集做
#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<cstring>
#define maxn 30005
int pre[maxn], num[maxn], a[maxn];
int n, m;
void initialize() {
for (int i = 0; i < n; i++) {
pre[i] = i;
num[i] = 1;
}
}
int find(int x) {
return x == pre[x] ? x : find(pre[x]);
}
void join(int x, int y) {
int fx = find(x);
int fy = find(y);
if (fx != fy) {
pre[fx] = fy;
num[fy] += num[fx];
}
}
int main() {
while (scanf_s("%d %d", &n, &m) != EOF && (n || m)) {
initialize();
while (m--) {
int t;
scanf_s("%d", &t);
for (int i = 0; i < t; i++) {
scanf_s("%d", &a[i]);
}
for (int i = 0; i < t-1; i++) {
join(a[i], a[i + 1]);
}
}
int s = find(0);
printf("%d\n", num[s]);
}
return 0;
}
```<God help those who help themselves>