Little Elephant and Filling
All submissions for this problem are available.
A Little Elephant from the Zoo of Lviv likes lucky strings, i.e., the strings that consist only of the lucky digits 4 and 7.
The Little Elephant has the string S such that each character in S is either the lucky digit (4 or 7) or the question mark ?. He can replace each question mark with one of the lucky digits in order to obtain the lucky string. He wants to know the number of different ways he can do this such that the resulting lucky string has no more than K different substrings. Help him and find this number. Note, that he need to replace all question marks.
Consider some example. From the string 47?4? we can obtain four lucky strings by replacing question marks with the lucky digits: 47444, 47447, 47744 and 47747. The corresponding numbers of different substrings are 11, 11, 12 and 11. For example, all different substrings of the string 47447 are 4, 7, 44, 47, 74, 447, 474, 744, 4744, 7447 and 47447.
Let S be some lucky string. Then
- |S| denotes the length of the string S;
- S[i] (1 ≤ i ≤ |S|) denotes the ith character of S (the numeration of characters starts from 1);
- The string T of the length M is called a substring of S if for some k from 0 to |S| - M we have
T = S[k + 1], T = S[k + 2], ..., T[M] = S[k + M].
The first line of the input file contains a single positive integer T, the number of test cases. T test cases follow. The first line of each test case contains two space separated integers N and K. The second line contains the string S of the length N.
For each test case output a single line containing the answer for the corresponding test case.
1 ≤ T ≤ 4747
1 ≤ N, K ≤ 50
For each string S from the input file we have that |S| = N and each character in S is either the lucky digit (4 or 7) or the question mark ?.
Input: 2 2 2 ?? 3 7 ?4? Output: 2 4
|Tags||cook22, medium, witua|
|Time Limit:||0.275 sec|
|Source Limit:||50000 Bytes|
|Languages:||C, CPP14, JAVA, PYTH, PYTH 3.5, CS2, PAS fpc, PAS gpc, RUBY, PHP, GO, NODEJS, HASK, SCALA, D, PERL, FORT, WSPC, ADA, CAML, ICK, BF, ASM, CLPS, PRLG, ICON, SCM qobi, PIKE, ST, NICE, LUA, BASH, NEM, LISP sbcl, LISP clisp, SCM guile, JS, ERL, TCL, PERL6, TEXT, CLOJ, FS|
Fetching successful submissions
If you are still having problems, see a sample solution here.