OJ-Problems-Source/HDOJ/4055_autoAC.cpp

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
const int N=1005;
const int mod=1000000007;
char str[N];
int dp[N][N],sum[N][N];
int main()
{
    while(scanf("%s",str+2)!=EOF)
    {
        memset(dp,0,sizeof(dp));
        memset(sum,0,sizeof(sum));
        int n=(int)strlen(str+2);
        dp[1][1]=sum[1][1]=1;
        for(int i=2;i<=n+1;i++)
        {
            for(int j=1;j<=i;j++)
            {
                if(str[i]=='I'||str[i]=='?') dp[i][j]=(dp[i][j]+sum[i-1][j-1])%mod;
                if(str[i]=='D'||str[i]=='?') 
                {
                    int tmp=((sum[i-1][i-1]-sum[i-1][j-1])%mod+mod)%mod;
                    dp[i][j]=(dp[i][j]+tmp)%mod;
                }
                sum[i][j]=(dp[i][j]+sum[i][j-1])%mod;
            }
        }
        printf("%d\n",sum[n+1][n+1]);
    }
    return 0;
}