% 2017 Qualification Round, Problem A, in Picat, by Afa Zhou
% https://code.google.com/codejam/contest/3264486/dashboard#s=p0
% Oversized Pancake Flipper

import util.

main =>
    T = read_line().to_int(),
    foreach (TC in 1..T)
        [Str,KStr] = read_line().split(),
        K = to_int(KStr),
        dc(TC,Str,len(Str),K,0)                        
    end.

dc(TC,Str,Len,K,N), Len < K =>
    (string_of(Str,'+') ->
        printf("Case #%w: %w\n", TC, N)
    ;
        printf("Case #%w: IMPOSSIBLE\n", TC)
    ).
dc(TC,['+'|Str],Len,K,N) =>
    dc(TC,Str,Len-1,K,N).
dc(TC,[_|Str],Len,K,N) =>
    divide(Str,K-1,L1,L2),
    flip(L1,FL1),
    dc(TC,FL1++L2,Len-1,K,N+1).

divide(L,0,L1,L2) => L1 = [], L2 = L.
divide([H|L],N,L1,L2) => L1 = [H|L1R], divide(L,N-1,L1R,L2).

string_of([],_) => true.
string_of([Ch|Str],Ch) =>
    string_of(Str,Ch).

flip(L,FL) => FL = [cond(Ch=='+','-','+') : Ch in L].

    

picat-lang.org