如何迭代锯齿状数组？

1 2 3
4 5 6
7 8 9

for i in range(len(array)):
    for j in range(len(array[i])):
        print(array[i][j])

step = 1
for i in range(len(array)):
    for j in range(len(array[i])):
        print(array[i][j])
    step *= -1

step = 1
for i in range(len(array)):
    for j in range(len(array[i])):
        print(array[i][j])
    step *= -1

step = 1
result = [array[i][j] for i in range(len(array)) for j in range(len(array[i]))]