poj 3761 bubble sort (排列组合)

 

#include<cstdio>#include<cstring>#define ll long long#define mod 20100713const int maxn=1000005;ll a[maxn];ll poww(ll x,int n){    ll ret=1;    while(n)    {        if(n&1)            ret=ret*x%mod;        n>>=1;        x=x*x%mod;    }    return ret;}int main(){    a[0]=1;    for(int i=1;i<maxn;i++)        a[i]=a[i-1]*i%mod;    int T;    scanf("%d",&T);    while(T--)    {        int n,k;        scanf("%d%d",&n,&k);        ll ans=a[k]*(poww(k+1,n-k)-poww(k,n-k)+mod)%mod;        printf("%lld\n",ans);    }    return 0;}