BZOJ 2751 容易题

233

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxn 100050
#define mod 1000000007
using namespace std;
long long n,m,k,sum[maxn],cnt=0;
struct pnt
{
    long long x,y;
}p[maxn];
bool cmp(pnt x,pnt y) 
{
    if (x.x==y.x) return x.y<y.y;
    return x.x<y.x;
}
long long f_pow(long long a,long long b)
{
    a%=mod;b%=mod;
    long long ans=1,base=a;
    if (b==0) return 1;
    while (b)
    {
        if (b&1) ans=(ans*base)%mod;
        base=(base*base)%mod;
        b>>=1;
    }
    return ans%mod;
}
int main()
{
    scanf("%lld%lld%lld",&n,&m,&k);
    for (long long i=1;i<=k;i++)
        scanf("%lld%lld",&p[i].x,&p[i].y);
    sort(p+1,p+k+1,cmp);
    for (long long i=1;i<=k;i++)
    {
        if ((p[i].x==p[i-1].x) && (p[i].y==p[i-1].y)) continue;
        if (p[i].x!=p[i-1].x) cnt++;
        sum[cnt]=(sum[cnt]+p[i].y)%mod;    
    }
    long long ans=1;
    for (long long i=1;i<=cnt;i++) ans=(ans*sum[i])%mod;
    printf("%lld\n",(ans*f_pow(n*(n+1)/2,m-cnt))%mod);
    return 0;
}