def f(a,n):
if n < 0:
print('Something wrong.')
return False
if n == 0:
b = [[]]
return b
m = len(a)
y = []
for i in range(m):
x = [a[i]]
for j in f(a,n-1):
y.append(x+j)
return y
a = [1,2,3,4]
print(f(a,2))
这样就是正常的
def f(a,n):
if n < 0:
print('Something wrong.')
return False
if n == 0:
b = []
return b
m = len(a)
y = []
for i in range(m):
x = [a[i]]
for j in f(a,n-1):
y.append(x+j)
return y
a = [1,2,3,4]
print(f(a,2))
这样返回值就只有 []