comb

comb.py

def comb(n, k):
    if k == n:
        return [[1 for _ in range(n)]]
    if k > n:
        return False
    if k == 0:
        return [[0 for _ in range(n)]]
    if k == 1:
        ret = []
        for i in range(n):
            l = []
            for j in range(n):
                if i == j:
                    ele = 1
                else:
                    ele = 0
                l.append(ele)
            ret.append(list(l))
        return ret
    ret = []
    for i in range(n):
        rest = comb(n - i - 1, k - 1)
        if rest is False:
            continue
        l = []
        for j in range(i):
            l.append(0)
        l.append(1)
        for r in rest:
            ret.append(l + r)
    return ret


print(comb(1, 0))
print(comb(1, 1))
print(comb(2, 1))
print(comb(4, 1))
print(comb(2, 3))
print(comb(3, 2))
print(comb(4, 2))