Java solution 273 & 260

Author: gavinfish

java/_260SingleNumberIII.java

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+/**
+ * Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.
+ * 
+ * For example:
+ * 
+ * Given nums = [1, 2, 1, 3, 2, 5], return [3, 5].
+ * 
+ * Note:
+ * The order of the result is not important. So in the above example, [5, 3] is also correct.
+ * Your algorithm should run in linear runtime complexity. Could you implement it using only constant space complexity?
+ */
+public class _260SingleNumberIII {
+    public int[] singleNumber(int[] nums) {
+        int diff = 0;
+        for (int num : nums) {
+            diff ^= num;
+        }
+        diff &= -diff;
+        int[] result = { 0, 0 };
+        for (int num : nums) {
+            if ((num & diff) == 0) {
+                result[0] ^= num;
+            } else {
+                result[1] ^= num;
+            }
+        }
+        return result;
+    }
+}

java/_273IntegertoEnglishWords.java

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+import javax.swing.text.AbstractDocument.LeafElement;
+
+/**
+ * Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1.
+ * 
+ * For example,
+ * 123 -> "One Hundred Twenty Three"
+ * 12345 -> "Twelve Thousand Three Hundred Forty Five"
+ * 1234567 -> "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"
+ */
+public class _273IntegertoEnglishWords {
+    private static final String[] LESS_THAN_20 = { "", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight",
+            "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen",
+            "Nineteen" };
+    private static final String[] TENS = { "", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy",
+            "Eighty", "Ninety" };
+    private static final String[] THOUSANDS = { "", "Thousand", "Million", "Billion" };
+
+    public String numberToWords(int num) {
+        if (num == 0) {
+            return "Zero";
+        }
+        int i = 0;
+        String result = "";
+        while (num > 0) {
+            if (num % 1000 != 0) {
+                result = helper(num % 1000) + THOUSANDS[i] + " " + result;
+            }
+            num /= 1000;
+            i++;
+        }
+        return result.trim();
+    }
+
+    private String helper(int num) {
+        if (num == 0) {
+            return "";
+        } else if (num < 20) {
+            return LESS_THAN_20[num] + " ";
+        } else if (num < 100) {
+            return TENS[num / 10] + " " + helper(num % 10);
+        } else {
+            return LESS_THAN_20[num / 100] + " Hundred " + helper(num % 100);
+        }
+    }
+}