updating readme.

051/README.md

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+## on the one hand... 
+
+...this is a badly-worded question, and that made the process a bit frustrating.
+
+After hours of developing and implementing a solution and debugging it so it worked on the examples,
+I still could not find a number with a pool of size 8. It took me a long time to realize that 
+the problem does not specify the number of `*` digits. I had been assuming 2.
+
+'''
+Find the smallest prime which, by replacing 
+part of the number (not necessarily adjacent 
+digits) with the same digit, is part of an 
+eight prime value family.
+'''
+
+So, whereas I wrote one program (the test program) to handle the one-star case `*3`, 
+then wrote an expanded version to handle the two-star case `X*X*XX`,
+and one that used recursion and all kinds of complicated mechanisms,
+instead, I should have just been writing a program to generate prime 
+numbers and look for patterns.
+
+Fortunately, the fix was trivial in this case. But it was a good illustration
+of why it's better not to waste a lot of time on the problems 
+you get stuck on. Often, there is ambiguity in the 
+problem statement that's entirely an artifact of the puzzle problem mentality.
+
+## on the other hand...
+
+...here are the timing comparisons for my own program, compared to a Python version from the web:
+
+```
+$ time java PrimeDigitReplacement3
+real	0m0.938s
+user	0m2.118s
+sys	0m0.124s
+
+$ time python from_the_internet.py
+real	0m11.727s
+user	0m11.335s
+sys	0m0.130s
+```
+
+Factor of 10 better? Not bad.
+