ans = (m+n)!*(m-n+1)/(m+1).
大数乘小数，大数除小数。
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1 /* 2 Author:Zhaofa Fang 3 Lang:C++ 4 */ 5 #include <cstdio> 6 #include <cstdlib> 7 #include <sstream> 8 #include <iostream> 9 #include <cmath> 10 #include <cstring> 11 #include <algorithm> 12 #include <string> 13 #include <utility> 14 #include <vector> 15 #include <queue> 16 #include <stack> 17 #include <map> 18 #include <set> 19 using namespace std; 20 21 typedef long long ll; 22 #define DEBUG(x) cout<< #x << ':' << x << endl 23 #define REP(i,n) for(int i=0;i < (n);i++) 24 #define FOR(i,s,t) for(int i = (s);i <= (t);i++) 25 #define FORD(i,s,t) for(int i = (s);i >= (t);i--) 26 #define PII pair<int,int> 27 #define PB push_back 28 #define MP make_pair 29 #define ft first 30 #define sd second 31 #define lowbit(x) (x&(-x)) 32 #define INF (1<<30) 33 34 int p[1000],q[1000]; 35 36 void print(int a[]) 37 { 38 int k = 999; 39 while(k>=0 && !a[k])k--; 40 FORD(i,k,0)printf("%d",a[i]); 41 puts(""); 42 } 43 void pro_Aa(int a[],int b) 44 { 45 int c[1000]={0}; 46 int e = 0; 47 int k = 0; 48 while(b) 49 { 50 for(int j=0;j+k<1000;j++) 51 { 52 int tmp = a[j] * (b%10); 53 int tmp1 = tmp + c[j+k] + e; 54 c[j+k] = (tmp1)%10; 55 e = (tmp1)/10; 56 } 57 b /= 10;k++; 58 } 59 REP(j,1000)a[j]=c[j]; 60 } 61 void div(int a[],int b) 62 { 63 int k = 999; 64 while(k>=0 && !a[k])k--; 65 int e = 0; 66 FORD(i,k,0) 67 { 68 int tmp = e*10 + a[i]; 69 a[i] = tmp/b; 70 e = tmp%b; 71 } 72 } 73 int main() 74 { 75 //freopen("in","r",stdin); 76 //freopen("output.txt","w",stdout); 77 int m,n; 78 int cas = 0; 79 while(~scanf("%d%d",&m,&n)) 80 { 81 if(!m && !n)break; 82 printf("Test #%d:\n",++cas); 83 if(m < n) 84 { 85 puts("0"); 86 continue; 87 } 88 memset(p,0,sizeof(p)); 89 p[0] = 1; 90 FORD(i,m+n,2)pro_Aa(p,i); 91 pro_Aa(p,m-n+1); 92 div(p,m+1); 93 print(p); 94 } 95 return 0; 96 }