【python 思路】题目：有1、2、3、4个数字，能组成多少个互不相同且无重复数字的三位数？都是多少？

# encoding:utf-8
# p001_1234threeNums.py

def threeNums():
    ‘‘‘题目：有1、2、3、4个数字，能组成多少个互不相同且无重复数字的三位数？都是多少？‘‘‘
    print None
    count = 0
    nums = []
    for index1 in xrange(1,5):
        for index2 in xrange(1,5):
            for index3 in xrange(1,5):
                if index1 != index2 and index1 != index3 and index2 != index3:
                    num = 100 * index1 + 10 * index2 + index3 
                    if num not in nums:
                        nums.append(num)
                        count += 1
    print count
    print nums

# threeNums()
# 在四个数中任意剔除一个，剩下三个的所有组合
import copy
def threeNums_method1():
    ‘‘‘take out a digit from the four digits‘‘‘
    L = [i for i in xrange(1,5)]
    print L
    cnt = 0
    for index in xrange(4):
        L1 = L[:]
        del L1[index]
        # L1 = L[0:index]+L[index+1:4]
        # print L1
        for index1 in xrange(3):
            print ‘%d%d%d‘%(L1[index1%3],L1[(index1+1)%3],L1[(index1+2)%3])
            cnt += 1
    print ‘count : %d‘%cnt

threeNums_method1()