Count the Sheep 思维题

Altough Skipping the class is happy, the new term still can drive luras anxious which is of course because of the tests! Luras became worried as she wanted to skip the class, as well as to attend the BestCoder and also to prepare for tests at the same time.

However, As the result of preparing for tests, luras had no time to
practice programing. She didn't want to lose her rating after attending
BC. In the end, she found BCround92's writer snowy_smile for help,
asking him to leak her something.

Snowy_smile wanted to help while not leaking the problems. He told
luras, the best thing to do is to take a good rest according to the
following instructions first.

"Imagine you are on the endless grassland where there are a group
of sheep. And n sheep of them are silent boy-sheep while m sheep are
crying girl-sheep. And there are k friend-relationships between the
boy-sheep and girl-sheep.Now You can start from any sheep, keep counting
along the friend relationship. If you can count 4 different sheep, you
will exceed 99% sheep-counters and fall asleep."

Hearing of the strange instructions, luras got very shocked. Still,
she kept counting. Sure enough, she fell asleep after counting 4
different sheep immediately. And, she overslept and missed the BestCoder
in the next day. At a result, she made it that not losing her rating in
the BCround92!!!

However, you don't have the same good luck as her. Since you have
seen the 2nd problem, you are possible to have submitted the 1st problem
and you can't go back.

So, you have got into an awkward position. If you don't AC this problem, your rating might fall down.

You question is here, please, can you tell that how many different 4-sheep-counting way luras might have before her sleep?

In another word, you need to print the number of the "A-B-C-D"
sequence, where A-B, B-C, C-D are friends and A,B,C,D are different.

InputThe first line is an integer T which indicates the case number.

and as for each case, there are 3 integers in the first line which
indicate boy-sheep-number, girl-sheep-number and
friend-realationship-number respectively.

Then there are k lines with 2 integers x and y in each line, which
means the x-th boy-sheep and the y-th girl-sheep are friends.

It is guaranteed that——

There will not be multiple same relationships.

1 <= T <= 1000

for 30% cases, 1 <= n, m, k <= 100

for 99% cases, 1 <= n, m, k <= 1000

for 100% cases, 1 <= n, m, k <= 100000OutputAs for each case, you need to output a single line.

there should be 1 integer in the line which represents the number of the counting way of 4-sheep-sequence before luras's sleep.Sample Input

3
2 2 4
1 1
1 2
2 1
2 2
3 1 3
1 1
2 1
3 1
3 3 3
1 1
2 1
2 2

Sample Output

8
0
2

这道题让我想到了二分图，离散刚学的，就是两边元素之间有边连接，各边元素之间无连接，要找出4个元素满足，A-B,B-C,C-D，注意一下，ABCD满足的话，DCBA也满足，可以考虑分析每一对男女，看看男的有几个女朋友，女的有几个男朋友，各自减一相乘就好了，有点像排列组合，最后再乘2，就ok。

代码：

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
using namespace std;

#define init(a)  memset(a,0,sizeof(a))
struct rela
{
    int x,y;
}re[];
int main()
{
    int t,n,m,k,x,y;
    long long ans;
    int b[],g[];
    cin>>t;
    while(t--)
    {
        scanf("%d%d%d",&n,&m,&k);
        init(b);
        init(g);
        ans=;
        for(int i=;i<k;i++)
        {
            scanf("%d%d",&x,&y);
            b[x]++;
            g[y]++;
            re[i].x=x,re[i].y=y;
        }
        for(int i=;i<k;i++)
        {
            ans+=(b[re[i].x]-)*(g[re[i].y]-);
        }
        cout<<ans*<<endl;
    }
}