How Many Tables

How Many Tables

Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 65536/32768K (Java/Other)

Total Submission(s) : 8   Accepted Submission(s) : 3

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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

并查集，找出多少个集合

#include<stdio.h>
int father[1005],depth[1005];
void init()
{
    int i;
    for(i = 1; i < 1005;i ++)
    {
        father[i] = i;
        depth[i] = 0;
    }
}

int find(int x)
{
    if(x==father[x])
        return x;
    else
        return father[x] = find(father[x]);
}

void unit(int x,int y)
{
    x = find(x);
    y = find(y);
    if(x==y)
        return ;
    if(depth[x]<depth[y])
    {
        father[x] = father[y];

    }
    else
    {
        if(depth[x]>depth[y])
            father[y] = father[x];
        else
        {
            father[x] = father[y];
            depth[y]++;
        }
    }
}

int main()
{
    int T,n,m,gr,j,a,b;
    scanf("%d",&T);
    while(T--)
    {
        gr = 0;
        init();
        scanf("%d%d",&n,&m);
        while(m--)
        {
            scanf("%d%d",&a,&b);
            unit(a,b);
        }
        for(j = 1;j <= n;j ++)
        {
            if(j == father[j])
                gr++;
        }
        printf("%d\n",gr);
    }
    return 0;
}