HDU 4055 DP

I am not very familiar with such questions .. Injury, look at others

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 1 # Include <stdio. h>
 2 # Include < String . H>
 3   # Define Maxn 1010
 4   Int DP [maxn] [maxn];
 5   Int Sum [maxn] [maxn];
 6   Const  Int MoD = 1000000007 ;
 7   Int Main ()
 8 {
 9       Int I, J;
 10       Char S [maxn];
 11       While (Scanf ( "  % S  " , S )! = EOF)
 12 {
 13           Int N = strlen (s );
 14 Memset (DP, 0 , Sizeof (DP ));
 15 Memset (sum, 0 , Sizeof (SUM ));
 16           For (I = 1 ; I <= N +1 ; I ++) sum [ 0 ] [I] = 1 ;
 17           For (I = 1 ; I <= N; I ++)
 18 {
 19               For (J = 1 ; J <= I + 1 ; J ++)
 20 {
21                   If (S [I- 1 ] = '  I  ' | S [I- 1 ] = '  ?  ' )
 22 {
 23 DP [I] [J] + = sum [I- 1 ] [J- 1 ];
 24 }
 25                   If (S [I- 1 ] = '  D  ' | S [I- 1 ] = '  ?  ' )
 26 {
 27 DP [I] [J] + = (sum [I-1 ] [I]-sum [I- 1 ] [J- 1 ]);
 28 DP [I] [J] = (DP [I] [J] + mod) % MOD;
 29 }
 30 Sum [I] [J] + = (sum [I] [J- 1 ] + Dp [I] [J]) % MOD;
 31 }
 32 }
 33           Int Ans = 0 ;
 34           For (I = 0 ; I <= N + 1 ; I ++)
 35 Ans = (ANS + dp [N] [I]) % MOD;
 36 Printf ( "  % D \ n  " , ANS );
 37 }
 38      Return   0 ;
 39 }