Заполнить матрицу зигзагом

def f(n):
    res = []
    k = 1
    for r in range(n):
        row = []
        for c in range(n):
            row.append(k)
            k += 1
        if r % 2 != 0:
            res.append(row[::-1])
        else:
            res.append(row)
    return res


a = f(5)
for x in a:
    print(x)