poj 1850 Code

组合数学！！！

详情见：http://hi.baidu.com/lxyzmnwvhokptur/item/18c806469a668fe31e19bc1a#0

 1 #include<iostream>
 2 #include<stdio.h>
 3 #include<algorithm>
 4 #include<iomanip>
 5 #include<cmath>
 6 #include<cstring>
 7 #include<vector>
 8 #define ll __int64
 9 #define pi acos(-1.0)
10 #define MAX 50000
11 using namespace std;
12 char a[10];
13 int C(int n,int m){
14     int sum =1;
15     for (int i=n;i>n-m;i--) sum*=i;
16     for (int j=1;j<=m;j++) sum /=j;
17     return sum;
18 }
19 int main(){
20     int i,j,len,sum;
21     while(cin>>a){
22         sum=0;
23         len = strlen(a);
24         if (len == 1){
25             if (a[0]>='a'&&a[0]<='z')
26                 cout<<a[0]-'a'+1<<endl;
27             else cout<<0<<endl;
28             continue;
29         }
30         for (i=1;i<len;i++){
31             if (a[i]<=a[i-1])
32                 break;
33         }
34         if (i!=len){
35             cout<<0<<endl;
36             continue;
37         }
38         for (i=1;i<len;i++)
39             sum += C(26,i);
40         for (j=1;j<a[0]-'a'+1;j++)
41                 sum += C(26-j,len-1);
42         for (i=1;i<len;i++){
43             for (j=a[i-1]+2-'a';j<a[i]-'a'+1;j++)
44                 sum += C(26-j,len-i-1);
45         }
46         cout<<++sum<<endl;
47     }
48     return 0;
49 }

 

posted @ 2013-07-28 16:58  _随心所欲_  阅读(167)  评论(0)  编辑  收藏  举报