add BullsAndCows299

Author: fluency03

Diff for: README.md

@@ -32,11 +32,11 @@
 
 
 
-# Total: 101
+# Total: 104
 
 | Easy | Medium | Hard |
 |:----:|:------:|:----:|
-|  18  |   61   |  24  |
+|  18  |   62   |  24  |
 
 
 | Question | Solution | Difficulty |
@@ -123,6 +123,7 @@
 | [273. Integer to English Words](https://leetcode.com/problems/integer-to-english-words/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/IntegerToEnglishWords273.java) | Hard |
 | [274. H-Index](https://leetcode.com/problems/h-index/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/IntegerToEnglishWords273.java) | Medium |
 | [283. Move Zeroes](https://leetcode.com/problems/move-zeroes/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/MoveZeroes283.java) | Easy |
+| [299. Bulls and Cows](https://leetcode.com/problems/bulls-and-cows/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/BullsAndCows299.java) | Medium |
 | [301. Remove Invalid Parentheses](https://leetcode.com/problems/remove-invalid-parentheses/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/RemoveInvalidParentheses301.java) | Hard |
 | [310. Minimum Height Trees](https://leetcode.com/problems/minimum-height-trees/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/MinimumHeightTrees310.java) | Medium |
 | [315. Count of Smaller Numbers After Self](https://leetcode.com/problems/count-of-smaller-numbers-after-self/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/CountOfSmallerNumbersAfterSelf315.java) | Hard |

Diff for: src/BullsAndCows299.java

@@ -0,0 +1,120 @@
+/**
+ * You are playing the following Bulls and Cows game with your friend:
+ * You write down a number and ask your friend to guess what the number is.
+ * Each time your friend makes a guess, you provide a hint that indicates
+ * how many digits in said guess match your secret number exactly in both digit
+ * and position (called "bulls") and how many digits match the secret number
+ * but locate in the wrong position (called "cows"). Your friend will use
+ * successive guesses and hints to eventually derive the secret number.
+ *
+ * Bulls and Cows https://en.wikipedia.org/wiki/Bulls_and_Cows
+ *
+ * For example:
+ *
+ * Secret number:  "1807"
+ * Friend's guess: "7810"
+ *
+ * Hint: 1 bull and 3 cows. (The bull is 8, the cows are 0, 1 and 7.)
+ * Write a function to return a hint according to the secret number and
+ * friend's guess, use A to indicate the bulls and B to indicate the cows.
+ * In the above example, your function should return "1A3B".
+ *
+ * Please note that both secret number and friend's guess may contain duplicate digits, for example:
+ *
+ * Secret number:  "1123"
+ * Friend's guess: "0111"
+ *
+ * In this case, the 1st 1 in friend's guess is a bull, the 2nd or 3rd 1 is a
+ * cow, and your function should return "1A1B".
+ *
+ * You may assume that the secret number and your friend's guess only contain
+ * digits, and their lengths are always equal.
+ */
+
+
+public class BullsAndCows299 {
+    public String getHint(String secret, String guess) {
+
+        Map<Character, Integer> secrets = new HashMap<>();
+        Map<Character, Integer> guesses = new HashMap<>();
+
+        Map<String, Integer> counts = new HashMap<>();
+        counts.put("bull", 0);
+        counts.put("cows", 0);
+
+        List<Integer> left = new ArrayList<>();
+
+        for (int i=0; i<guess.length(); i++) {
+            Character c1 = secret.charAt(i);
+            Character c2 = guess.charAt(i);
+
+            if (c1.equals(c2)) {
+                counts.put("bull", counts.get("bull")+1);
+            } else {
+                secrets.put(c1, secrets.getOrDefault(c1, 0)+1);
+                guesses.put(c2, guesses.getOrDefault(c2, 0)+1);
+            }
+        }
+
+        for (Map.Entry<Character, Integer> e: guesses.entrySet()) {
+            if (secrets.containsKey(e.getKey())) {
+                counts.put("cows", counts.get("cows") + Math.min(secrets.get(e.getKey()), e.getValue()));
+            }
+        }
+
+        return String.format("%dA%dB", counts.get("bull"), counts.get("cows"));
+    }
+
+
+    public String getHint2(String secret, String guess) {
+
+        Map<Character, Integer> secrets = new HashMap<>();
+        Map<Character, Integer> guesses = new HashMap<>();
+
+        Map<String, Integer> counts = new HashMap<>();
+        counts.put("bull", 0);
+        counts.put("cows", 0);
+
+        for (int i=0; i<guess.length(); i++) {
+            Character c1 = secret.charAt(i);
+            Character c2 = guess.charAt(i);
+
+            if (c1.equals(c2)) {
+                counts.put("bull", counts.get("bull")+1);
+            } else {
+                if (secrets.containsKey(c2) && secrets.get(c2) > 0) {
+                    secrets.put(c2, secrets.get(c2)-1);
+                    counts.put("cows", counts.get("cows")+1);
+                } else {
+                    guesses.put(c2, guesses.getOrDefault(c2, 0)+1);
+                }
+                if (guesses.containsKey(c1) && guesses.get(c1) > 0) {
+                    guesses.put(c1, guesses.get(c1)-1);
+                    counts.put("cows", counts.get("cows")+1);
+                } else {
+                    secrets.put(c1, secrets.getOrDefault(c1, 0)+1);
+                }
+            }
+        }
+
+        return String.format("%dA%dB", counts.get("bull"), counts.get("cows"));
+    }
+
+    /**
+     * https://discuss.leetcode.com/topic/28463/one-pass-java-solution
+     */
+    public String getHint3(String secret, String guess) {
+        int bulls = 0;
+        int cows = 0;
+        int[] numbers = new int[10];
+        for (int i = 0; i<secret.length(); i++) {
+            if (secret.charAt(i) == guess.charAt(i)) bulls++;
+            else {
+                if (numbers[secret.charAt(i)-'0']++ < 0) cows++;
+                if (numbers[guess.charAt(i)-'0']-- > 0) cows++;
+            }
+        }
+        return bulls + "A" + cows + "B";
+    }
+
+}