Solving 15Puzzle with Julia - optimization

Question

I'm trying to use Julia to solve the common tile game 15 Puzzle using Julia using A* algorithm. I am quite new to the language and my style may seem very C like. When I try the following code, I run out of memory. I'm not sure if its related to the use of a pointer style in my structs or just bad design.
struct Node
parent
f::Int64
board::Array{Int64,1}
end
function findblank(A::Array{Int64,1})
x = size(A,1)
for i = 1:x
if A[i] == x
return i
end
end
return -1
end
function up(A::Array{Int64,1})
N = size(A,1)
Nsq = isqrt(N)
blank = findblank(A)
B = copy(A)
if blank / Nsq <= 1
return nothing
end
B[blank-Nsq],B[blank] = B[blank],B[blank-Nsq]
return B
end
function down(A::Array{Int64,1})
N = size(A,1)
Nsq = isqrt(N)
blank = findblank(A)
B = copy(A)
if (blank / Nsq) > (Nsq -1)
return nothing
end
B[blank+Nsq],B[blank] = B[blank],B[blank+Nsq]
return B
end
function left(A::Array{Int64,1})
N = size(A,1)
Nsq = isqrt(N)
blank = findblank(A)
B = copy(A)
if (blank % Nsq) == 1
return nothing
end
B[blank-1],B[blank] = B[blank],B[blank-1]
return B
end
function right(A::Array{Int64,1})
N = size(A,1)
Nsq = isqrt(N)
blank = findblank(A)
B = copy(A)
if (blank % Nsq) == 0
return nothing
end
B[blank+1],B[blank] = B[blank],B[blank+1]
return B
end
function manhattan(A::Array{Int64,1})
N = size(A,1)
Nsq = isqrt(N)
r = 0
for i in 1:N
if (A[i]==i || A[i]==N)
continue
end
row1 = floor((A[i]-1) / Nsq)
col1 = (A[i]-1) % Nsq
row2 = floor((i-1) / Nsq)
col2 = (i-1) % Nsq
r+= abs(row1 - row2) + abs(col1 - col2)
end
return r
end
# start = [1,2,3,4,5,6,7,9,8]
# start = [6,5,4,1,7,3,9,8,2] #26 moves
start = [7,8,4,11,12,14,10,15,16,5,3,13,2,1,9,6] # 50 moves
goal = [x for x in 1:length(start)]
# println("The manhattan distance of $start is $(manhattan(start))")
g = 0
f = g + manhattan(start)
pq = PriorityQueue()
actions = [up,down,left,right]
dd = Dict{Array{Int64,1},Int64}()
snode = Node(C_NULL,f,start)
enqueue!(pq,snode,f)
pos_seen = 0
moves = 0
while (!isempty(pq))
current = dequeue!(pq)
if haskey(dd,current.board)
continue
else
push!(dd, current.board =>current.f)
end
if (current.board == goal)
while(current.board != start)
println(current.board)
global moves +=1
current = current.parent[]
end
println(start)
println("$start solved in $moves moves after looking at $pos_seen positions")
break
end
global pos_seen+=1
global g+=1
for i in 1:4
nextmove = actions[i](current.board)
if (nextmove === nothing || nextmove == current.board || haskey(dd,nextmove))
continue
else
global f = g+manhattan(nextmove)
n = Node(Ref(current),f,nextmove)
enqueue!(pq,n,f)
end
end
end
println("END")