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有四个数字：1、2、3、4，能组成多少个互不相同且无重复数字的三位数？各是多少？
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import itertools


def test001():
    arr = []
    for a in range(1, 5):
        for b in range(1, 5):
            for c in range(1, 5):
                num = 100*a+10*b+c
                if a != b and b != c and a != c and num not in arr:
                    arr.append(num)
    print(len(arr), arr)

test001()
print("="*10)

方法二

def test002():
    res_list = list(itertools.permutations([1, 2, 3, 4], 3))
    print(res_list)
    # result = [100*t[0]+10*t[1]+t[2] for t in res_list]
    result = [int(''.join(map(str, i))) for i in res_list]
    print(len(result), result)

test002()