w****f 发帖数: 684 | 1 5 'A'
4 'B'
3 'C'
Q: how many unique 5-letter words can be formed?
It took me long time to thinks, but interviewer didn't happy with my
final answer.
If all 5 'A', 'B', 'C', the combination is 3^5 = 243;
missing 5'B', 1
missing 5'C', 1
missing (A/B) 4C, 10
total is 3^5 -1 -1 -10 = 231;
do I get it right (after interview)?
| d**u 发帖数: 1065 | | s****r 发帖数: 47 | 3 我认为楼主的答案是对的。
【在 w****f 的大作中提到】 : 5 'A' : 4 'B' : 3 'C' : Q: how many unique 5-letter words can be formed? : It took me long time to thinks, but interviewer didn't happy with my : final answer. : If all 5 'A', 'B', 'C', the combination is 3^5 = 243; : missing 5'B', 1 : missing 5'C', 1 : missing (A/B) 4C, 10
| w****f 发帖数: 684 | 4 可惜在最后,
我只是 给出了 3^5 - 1 -1 -10
没有给出答案 是 231
【在 w****f 的大作中提到】 : 5 'A' : 4 'B' : 3 'C' : Q: how many unique 5-letter words can be formed? : It took me long time to thinks, but interviewer didn't happy with my : final answer. : If all 5 'A', 'B', 'C', the combination is 3^5 = 243; : missing 5'B', 1 : missing 5'C', 1 : missing (A/B) 4C, 10
| w****f 发帖数: 684 | 5 What is general formula for this unique letter?
Numerical try: 12! / (5!*4!*3!)/5! =231 , 数字巧合? 还是有规律?
Total permutation is 12!
duplicate : 5! * 4! * 3!
then what about last 5! ?
Another try: 12!/7! / (5!*4!*3!)/5! =5.5 failed. | l*********8 发帖数: 4642 | 6 巧合吧
【在 w****f 的大作中提到】 : What is general formula for this unique letter? : Numerical try: 12! / (5!*4!*3!)/5! =231 , 数字巧合? 还是有规律? : Total permutation is 12! : duplicate : 5! * 4! * 3! : then what about last 5! ? : : Another try: 12!/7! / (5!*4!*3!)/5! =5.5 failed.
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