### Problem

The Game of Master Mind is played as follows:

The computer has four slots containing balls that are red (R), yellow (Y), green (G) or blue (B). For example, the computer might have RGGB (e.g., Slot #1 is red, Slots #2 and #3 are green, Slot #4 is blue).

You, the user, are trying to guess the solution You might, for example, guess YRGB.

When you guess the correct color for the correct slot, you get a “hit” If you guess a color that exists but is in the wrong slot, you get a “pseudo-hit”. For example, the guess YRGB has 2 hits and one pseudo hit.

For each guess, you are told the number of hits and pseudo-hits.

Write a method that, given a guess and a solution, returns the number of hits and pseudo-hits.

### Solution

1st scan, we can find out how many hits there are by comparing character by character. During this scan, we can also build a hashtable for all the characters in the solution. The second scan, we count how many characters in the guess are matched in the hashtable. The counts – hints is the pseudo-hits.public static class Result { public int hits; public int pseudoHits; }; public static Result masterMind(String guess, String solution) { Result res = new Result(); int solution_mask = 0; for (int i = 0; i < 4; ++i) { solution_mask |= 1 << (1 + solution.charAt(i) - 'A'); } for (int i = 0; i < 4; ++i) { if (guess.charAt(i) == solution.charAt(i)) { ++res.hits; } else if ((solution_mask & (1 << (1 + guess.charAt(i) - 'A'))) >= 1) { ++res.pseudoHits; } } return res; } //runner main public static void main(String[] args) { masterMind("YRGB", "RGGB"); }

Thanks.

**References**

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