[알고리즘 필수 기법] 조합, 순열

def comb(arr,n):
    result = []
    if n > len(arr):
        return result
    if n == 1:
        for i in arr:
            result.append([i])
    elif n > 1:
        for i in range(len(arr) - n + 1):
            for j in comb(arr[i + 1:], n - 1):
                result.append([arr[i]] + j)
    return result

 

def perm(arr,n):
    result = []
    if n > len(arr):
        return result
    if n == 1:
        for i in arr:
            result.append([i])
    elif n > 1:
        for i in range(len(arr)):
            ans = [i for i in arr]
            ans.remove(arr[i])
            for p in perm(ans, n-1):
                result.append([arr[i]]+p)
    return result