怎样学好哲学（lucas+费马小定理）

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<iostream>
 6 #define mod 1000003
 7 #define ll long long
 8 #define Q 2007 
 9 using namespace std;
10 
11 int n,m,q;
12 ll p[mod+7],inv[mod+7],dp[Q];
13 struct Node
14 {
15     int x,y;
16 }a[Q];
17 
18 bool cmp(Node x,Node y)
19 {
20     return x.x<y.x;
21 }
22 ll ksm(ll a,ll b)
23 {
24     ll ans=1;
25     while (b)
26     {
27         if (b&1) ans=a*ans%mod;
28         b/=2;
29         a=a*a%mod;
30     }
31     return ans;
32 }
33 ll Lucas_C(int n,int m)
34 {
35     if (n<m) return 0;
36     if (m==0) return 1;
37     if (n==m) return 1;
38     if (n<mod) return p[n]*inv[m]%mod*inv[n-m]%mod;
39     else return Lucas_C(n%mod,m%mod)*Lucas_C(n/mod,m/mod)%mod;
40 }
41 int main()
42 {
43     p[1]=1;
44     for (int i=2;i<=mod;i++)
45         p[i]=(p[i-1]*i)%mod;
46     for (int i=1;i<=mod;i++)
47         inv[i]=ksm(p[i],mod-2);
48     scanf("%d%d%d",&n,&m,&q);
49     
50     for (int i=1;i<=q;i++)
51         scanf("%d%d",&a[i].x,&a[i].y);
52     q++,a[q].x=n+1,a[q].y=m+1;
53     sort(a+1,a+q+1,cmp);
54     for (int i=1;i<=q;i++)
55     {
56         dp[i]=Lucas_C(a[i].y-1,a[i].x-1);
57         for (int j=1;j<i;j++)
58             if (a[i].x>a[j].x&&a[i].y>a[j].y)
59                 dp[i]=(dp[i]-dp[j]*Lucas_C(a[i].y-a[j].y-1,a[i].x-a[j].x-1)%mod+mod)%mod;            
60     }
61     printf("%lld",dp[q]);
62 }