It times out - is that expected?

```
def backtracking(n):
count = 0
x = []
q = []
q.append(x)
while len(q) > 0:
x = q.pop()
if len(x) == n:
count += 1
else:
for i in range(10):
y = x[:]
if i not in x:
y.append(i)
q.append(y)
elif len(y) < n and y[0] == 0:
count += 1
return count
```