# POJ 1611 The Suspects C语言版

POJ题解 3371浏览

Description

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.

Input

The input file contains several cases. Each test case begins with two integers n and m in a line, where n is the number of students, and m is the number of groups. You may assume that 0 < n <= 30000 and 0 <= m <= 500. Every student is numbered by a unique integer between 0 and n−1, and initially student 0 is recognized as a suspect in all the cases. This line is followed by m member lists of the groups, one line per group. Each line begins with an integer k by itself representing the number of members in the group. Following the number of members, there are k integers representing the students in this group. All the integers in a line are separated by at least one space.
A case with n = 0 and m = 0 indicates the end of the input, and need not be processed.

Output

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

Slyar:说下题目大意。一共有n个学生(编号0 至 n-1)，m个组，一个学生可以同时加入不同的组。现在有一种传染病，如果一个学生被感染，那么和他同组的学生都会被感染。现在已知0号学生被感染，问一共有多少个人被感染。

```#include
#include

/*
num[]存储节点所在集合元素的个数
father[]存储节点的父节点
*/
int num, father;

/* 初始化集合 */
void Make_Set(int x)
{
father[x] = -1;
num[x] = 1;
}

/* 查找x元素所在的集合，返回根节点 */
int Find_Set(int x)
{
/* 保存待查找值x */
int r = x, tmp;
/* 找到根节点r */
while (father[r] != -1)
{
r = father[r];
}
/* 压缩路径，将路径上所有r的子孙都连接到r上 */
while (x != r)
{
tmp = father[x];
father[x] = r;
x = tmp;
}
return x;
}

/* 合并a,b所在的集合 */
void Union_Set(int a, int b)
{
a = Find_Set(a);
b = Find_Set(b);
/* 如果两个元素在同一个集合则不需要合并 */
if (a == b) return;
/* 将小集合合并到大集合中，更新集合个数 */
if (num[a] <= num[b])
{
father[a] = b;
num[b] += num[a];
}
else
{
father[b] = a;
num[a] += num[b];
}
}

int main()
{
int a, b, n, m, t;
int i, j;
while (1)
{
scanf("%d%d", &n, &m);
if (n + m == 0) break;
for (i = 0; i < n; i++)
{
Make_Set(i);
}
for (i = 0; i < m; i++)
{
scanf("%d", &t);
scanf("%d", &a);
for (j = 1; j < t; j++)
{
scanf("%d", &b);
Union_Set(a, b);
}
}
printf("%d\n", num[Find_Set(0)]);
}
return 0;
}
```

```#include
#include

/* father[]存储节点的父节点，对于根节点x，father[x]为子孙数 */
int father;

/* 初始化集合 */
void Make_Set(int x)
{
father[x] = -1;
}

/* 查找x元素所在的集合，返回根节点 */
int Find_Set(int x)
{
/* 保存待查找值x */
int r = x, tmp;
/* 找到根节点r */
while (father[r] > 0)
{
r = father[r];
}
/* 压缩路径，将路径上所有r的子孙都连接到r上 */
while (x != r)
{
tmp = father[x];
father[x] = r;
x = tmp;
}
return x;
}

/* 合并a,b所在的集合 */
void Union_Set(int a, int b)
{
a = Find_Set(a);
b = Find_Set(b);
/* 如果两个元素在同一个集合则不需要合并 */
if (a == b) return;
/* 将小集合合并到大集合中(这里是负数比较)，更新集合个数*/
if (father[a] < father[b])
{
father[a] += father[b];
father[b] = a;
}
else
{
father[b] += father[a];
father[a] = b;
}
}

int main()
{
int i, j;
int a, b, n, m, t;
while (1)
{
scanf("%d%d", &n, &m);
if (n + m == 0) break;
for (i = 0; i < n; i++)
{
Make_Set(i);
}
for (i = 0; i < m; i++)
{
scanf("%d", &t);
scanf("%d", &a);
for (j = 1; j < t; j++)
{
scanf("%d", &b);
Union_Set(a, b);
}
}
/* 节点数目为负值 */
printf("%d\n", -father[Find_Set(0)]);
}
return 0;
}
```

### 网友最新评论 (4)

1. @ 编译器不同，运行时间不同，得到的时间不同。时间是浮云，不在乎...=_=
Slyar10年前 (2010-11-11)回复
2. 大牛，我拿你程序在POJ测了一下，是10ms，而非0ms。。。
匿名10年前 (2010-11-11)回复
3. 有些地方不是很懂，能不能一下你的QQ号，我想请教一下你，我的QQ493712874
gongzhi11年前 (2010-05-08)回复