Problem Solving (PS) | Re: The letters D, G, I, I , and T can be used to form 5-letter strings as

Just want to share my approach:

1. In this case, the 3 letter D,G,T can be calculated easily : 3! = 6.
2. The problem is only the remanining I : which must place with separation.
3. The best way to calculate the "I"
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