POJ 1850 Code

虽然有点水，不过做完还是有收获的

#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<stack>
#include<string>
#include<map>
#include<set>
#include<cmath>
#include<cassert>
#include<cstring>
#include<iomanip>
using namespace std;
#ifdef _WIN32
#define i64 __int64
#define out64 "%I64d\n"
#define in64 "%I64d"
#else
#define i64 long long
#define out64 "%lld\n"
#define in64 "%lld"
#endif
/************ for topcoder by zz1215 *******************/
#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)
#define FFF(i,a)        for( int i = 0 ; i < (a) ; i ++)
#define FFD(i,a,b)      for( int i = (a) ; i >= (b) ; i --)
#define S64(a)          scanf(in64,&a)
#define SS(a)           scanf("%d",&a)
#define LL(a)           ((a)<<1)
#define RR(a)           (((a)<<1)+1)
#define pb              push_back
#define CL(Q)           while(!Q.empty())Q.pop()
#define MM(name,what)   memset(name,what,sizeof(name))
#define MC(a,b)			memcpy(a,b,sizeof(b))
#define MAX(a,b)        ((a)>(b)?(a):(b))
#define MIN(a,b)        ((a)<(b)?(a):(b))
#define read            freopen("in.txt","r",stdin)
#define write           freopen("out.txt","w",stdout)

const int inf = 0x3f3f3f3f;
const i64 inf64 = 0x3f3f3f3f3f3f3f3fLL;
const double oo = 10e9;
const double eps = 10e-9;
const double pi = acos(-1.0);
const int maxc = 27;
const int maxn = 11;

i64 c[maxc][maxc];
i64 dp[maxn][maxc];
i64 f[maxn];
string s;

void init()
{
	MM(c,0);
	for(int i=0;i<maxc;i++)
	{
		c[i][0]=1;
		c[i][i]=1;
	}
	for(int i=1;i<maxc;i++)	
	{
		for(int j=1;j<i;j++)
		{
			c[i][j]=c[i-1][j-1]+c[i-1][j];
		}		
	}
	MM(dp,0);
	for(int i=1;i<maxn;i++)
	{
		dp[i][0]=0;
	}
	for(int i=1;i<maxn;i++)
	{
		for(int j=1;j<26;j++)
		{
			dp[i][j]=c[26-j][i-1];
		}	
	}
	MM(f,0);
	for(int i=1;i<maxn;i++)
	{
		f[i]=c[26][i];
	}
	for(int i=1;i<maxn;i++)
	{
		f[i]+=f[i-1];
	}
	return ;
}


i64 start()
{
	int len = s.length();
	int pre,now,pos;
	i64 ans=1;
	for(int i=len-1;i>=1;i--)
	{
		pos = len - i;
		pre = s[i-1]-'a';
		now = s[i]-'a';
		for(int x=now;x>pre+1;x--)
		{
			ans+=dp[pos][x];
		}
	}
	now = s[0]-'a';	
	for(int i=now;i>=1;i--)	
	{
		ans+=dp[len][i];
	}
	ans+=f[len-1];
	return ans;
}

bool can()
{
	int temp=-inf;
	for(int i=0;i<s.length();i++)
	{
		if(s[i]>temp && s[i]>='a' && s[i]<='z')
		{
			temp = s[i];
		}
		else
		{
			return false;
		}
	}
	return true;
}

int main()
{
	init();
	while(cin>>s)
	{
		if(can())	
		{
			cout<<start()<<endl;
		}
		else
		{	
			cout<<"0"<<endl;	
		}
	}
	return 0;
}