hdu 1133(卡特兰数)
题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=1133
卡特兰数的应用:( C(m+n, n) - C(m+n, m+1) ) * m! * n! 化简即 (m+n)! * (m-n+1) / (m+1)
string处理比较方便。。。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 #include<iostream> 2 #include<algorithm> 3 #include<string> 4 #include<vector> 5 using namespace std; 6 vector<string>vet; 7 8 string Mul(string &str,int n){ 9 string s=""; 10 int len=str.size(); 11 int c=0,l=0; 12 for(int i=len-1;i>=0;i--){ 13 c=l+(str[i]-'0')*n; 14 l=c/10; 15 s+=c%10+'0'; 16 } 17 while(l){ 18 s+=l%10+'0'; 19 l=l/10; 20 } 21 reverse(s.begin(),s.end()); 22 return s; 23 } 24 25 void Facs(){ 26 vet.push_back("0"); 27 vet.push_back("1"); 28 vet.push_back("2"); 29 string str="2"; 30 for(int i=3;i<=204;i++){ 31 str=Mul(str,i); 32 vet.push_back(str); 33 } 34 } 35 36 string Divide(string &str,int n){ 37 string s=""; 38 int len=str.size(); 39 int c=0,l=0; 40 for(int i=0;i<=len-1;i++){ 41 c=l*10+str[i]-'0'; 42 l=c%n; 43 c=c/n; 44 if(c==0&&s.size()==0)continue; 45 else s+=c+'0'; 46 } 47 return s; 48 } 49 50 int main(){ 51 Facs(); 52 int n,m; 53 int _case=1; 54 while(~scanf("%d%d",&m,&n)){ 55 if(n==0&&m==0)break; 56 printf("Test #%d:\n",_case++); 57 if(m<n){ 58 printf("0\n"); 59 continue; 60 } 61 string str=vet[n+m]; 62 str=Mul(str,m-n+1); 63 str=Divide(str,m+1); 64 cout<<str<<endl; 65 } 66 return 0; 67 }