Hdu 6016-Count the Sheep

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=6016

题目大意：中文题面http://bestcoder.hdu.edu.cn/contests/contest_chineseproblem.php?cid=748&pid=1002

题目思路：总共三条边， 枚举中间一条边。

代码如下：

#include<bits/stdc++.h>
using namespace std;

vector<int>vecm[100007], vecg[100007];
int a[100007], b[100007];
void solve()
{
    int n, m, k;
    scanf("%d%d%d", &n, &m, &k);
    int s = max(n, m);
    for(int i=1; i<=s; ++ i)
    {
        vecm[i].clear();
        vecg[i].clear();
    }
    for(int i=1; i<=k; ++ i)
    {
        scanf("%d %d", &a[i], &b[i]);
        vecm[a[i]].push_back(b[i]);
        vecg[b[i]].push_back(a[i]);
    }
    long long ans = 0;
    for(int i=1; i<=k; ++ i)
    {
        ans += (long long)(vecm[a[i]].size() - 1) * (long long)(vecg[b[i]].size() - 1);
    }
    printf("%I64d
", ans*2);
}

int main()
{
    int t;
    scanf("%d", &t);
    while(t--)
        solve();
    return 0;
}