1120 机器人走方格 V3

 1 #include<stdio.h>
 2 #include<algorithm>
 3 #include<iostream>
 4 #include<string.h>
 5 #include<queue>
 6 #include<math.h>
 7 using namespace std;
 8 const int mod = 10007;
 9 typedef long long LL;
10 LL N[10008];
11 LL quick(LL n,LL m);
12 LL lucas(LL n,LL m);
13 int main(void)
14 {
15     N[0] = 1;
16     int i,j;
17     for(i = 1; i <= 10007; i++)
18         N[i] = N[i-1]*(LL)i%mod;
19     LL n;
20     scanf("%lld",&n);n--;
21     if(n==0)printf("1\n");
22     else
23     {LL ask = lucas(2*n,n) - lucas(2*n,n-1);
24     ask = ask%mod + mod;
25     printf("%lld\n",2*ask%mod);}
26     return 0;
27 }
28 LL lucas(LL n,LL m)
29 {
30     if(m == 0)return 1;
31     LL x = n%mod;
32     LL y = m%mod;
33     if(y > x)
34         return 0;
35     LL ni = N[x-y]*N[y]%mod;
36     ni =quick(ni,mod-2);
37     ni = ni*N[x]%mod;
38     return ni*lucas(n/mod,m/mod);
39 }
40 LL quick(LL n,LL m)
41 {
42     LL ans = 1;
43     n %= mod;
44     while(m)
45     {
46         if(m&1)
47             ans = ans*n%mod;
48         n = n*n%mod;
49         m>>=1;
50     }
51     return ans;
52 }