标签：mit can 高度 题目 this acm 代码 class which
题目：
How Many Tables
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 41763 Accepted Submission(s): 20915
Problem Description
Today
is Ignatius‘ birthday. He invites a lot of friends. Now it‘s dinner
time. Ignatius wants to know how many tables he needs at least. You have
to notice that not all the friends know each other, and all the friends
do not want to stay with strangers.
One important rule for this
problem is that if I tell you A knows B, and B knows C, that means A, B,
C know each other, so they can stay in one table.
For example:
If I tell you A knows B, B knows C, and D knows E, so A, B, C can stay
in one table, and D, E have to stay in the other one. So Ignatius needs 2
tables at least.
Input
The
input starts with an integer T(1<=T<=25) which indicate the
number of test cases. Then T test cases follow. Each test case starts
with two integers N and M(1<=N,M<=1000). N indicates the number of
friends, the friends are marked from 1 to N. Then M lines follow. Each
line consists of two integers A and B(A!=B), that means friend A and
friend B know each other. There will be a blank line between two cases.
Output
For each test case, just output how many tables Ignatius needs at least. Do NOT print any blanks.
Sample Input
2
5 3
1 2
2 3
4 5
5 1
2 5
Sample Output
2
4
思路：
代码：
//按秩合并的并查集
#include <iostream>
int Find(int a[], int x)//找根
{
while(x != a[x])
{
x = a[x];
}
return x;
}
bool IsConnected(int a[], int x, int y)//判断是否已连接
{
return Find(a,x) == Find(a,y);
}
void Union(int a[], int b[], int x, int y)//合并两个树
{
int c = Find(a,x);
int d = Find(a,y);
if(b[c] < b[d])//小的树连到大的树上
a[c] = d;
else
{
a[d] = c;
if(b[c] == b[d])//若两个树高度相等，则合并后高度+1
b[c]++;
}
}
int main()
{
using namespace std;
int T;
cin >> T;
while(T--)
{
int N, M;
int x, y;
cin >> N >> M;
int num = N;
int * a = new int[N+1];
int * b = new int[N+1];//记录树的高度
for(int i = 0; i < N+1; i++)
{
a[i] = i;
b[i] = 1;
}
while(M--)
{
cin >> x >> y;
if(IsConnected(a,x,y))
continue;
Union(a,b,x,y);
num--;
}
printf("%d\n", num);
}
}
How Many Tables//并查集
标签：mit can 高度 题目 this acm 代码 class which
原文地址：https://www.cnblogs.com/w-j-c/p/9218929.html
