pony_express
``` ```
% 2017 Round 1B, Problem C, in Picat, by Afa Zhou
% Pony Express

import util.

main =>
foreach (TC in 1..T)
[N,Q] = [to_int(Token) : Token in read_line().split()],
HL = [],
foreach (_ in 1..N)
HL := [[to_int(Token) : Token in read_line().split()]|HL]
end,
HA = HL.reverse().to_array(),
M = new_array(N),
foreach (I in 1..N)
M[I] = {to_int(Token) : Token in read_line().split()}
end,
Fs = [],
foreach (I in 1..N)
Neibs = [J : J in 1..N, M[I,J] !== -1],
Fs := [\$neibs(I,Neibs)|Fs]
end,
cl_facts(Fs,[\$neibs(+,-)]),
Qs = [[to_int(Token) : Token in read_line().split()] : _ in 1..Q],
printf("Case #%w: ", TC),
foreach ([U,V] in Qs)
[E,S] = HA[U],
sol(U,V,E,S,HA,M,Time),
printf("%.6f ", Time)
end,
nl
end.

table (+,+,+,+,+,+,min)
sol(U,U,E,S,HA,M,Time) => Time = 0.
sol(U,V,E,S,HA,M,Time) ?=>
neibs(U,Neibs),
member(Next,Neibs),
Dist = M[U,Next],
E >= Dist,
sol(Next,V,E-Dist,S,HA,M,Time1),
Time = Time1+Dist/S.
sol(U,V,_E,_S,HA,M,Time) =>
[E,S] = HA[U],
sol(U,V,E,S,HA,M,Time).

``````