Added task 273.

Author: javadev

Diff for: src/main/java/s0273.integer.to.english.words/Solution.java

@@ -0,0 +1,71 @@
+package s0273.integer.to.english.words;
+
+public class Solution {
+
+    String[] ones =
+            new String[] {
+                "One ", "Two ", "Three ", "Four ", "Five ", "Six ", "Seven ", "Eight ", "Nine "
+            };
+    String[] teens =
+            new String[] {
+                "Ten ",
+                "Eleven ",
+                "Twelve ",
+                "Thirteen ",
+                "Fourteen ",
+                "Fifteen ",
+                "Sixteen ",
+                "Seventeen ",
+                "Eighteen ",
+                "Nineteen "
+            };
+    String[] twenties =
+            new String[] {
+                "Twenty ", "Thirty ", "Forty ", "Fifty ", "Sixty ", "Seventy ", "Eighty ", "Ninety "
+            };
+
+    String zero = "Zero";
+    String hundred = "Hundred ";
+    String thousand = "Thousand ";
+    String million = "Million ";
+    String billion = "Billion ";
+
+    public String numberToWords(int num) {
+        if (num == 0) return zero;
+
+        StringBuilder sb = new StringBuilder();
+
+        processThreeDigits(sb, num / 1_000_000_000, billion);
+        processThreeDigits(sb, num / 1_000_000, million);
+        processThreeDigits(sb, num / 1_000, thousand);
+        processThreeDigits(sb, num, null);
+
+        return sb.toString().trim();
+    }
+
+    private void processThreeDigits(StringBuilder sb, int input, String name) {
+        int threeDigit = input % 1000;
+
+        if (threeDigit > 0) {
+            if (threeDigit / 100 > 0) {
+                sb.append(ones[threeDigit / 100 - 1]);
+                sb.append(hundred);
+            }
+
+            if (threeDigit % 100 >= 20) {
+                sb.append(twenties[(threeDigit % 100) / 10 - 2]);
+                if (threeDigit % 10 > 0) {
+                    sb.append(ones[threeDigit % 10 - 1]);
+                }
+            } else if (threeDigit % 100 >= 10 && threeDigit % 100 < 20) {
+                sb.append(teens[threeDigit % 10]);
+            } else if (threeDigit % 100 > 0 && threeDigit % 100 < 10) {
+                sb.append(ones[threeDigit % 10 - 1]);
+            }
+
+            if (name != null) {
+                sb.append(name);
+            }
+        }
+    }
+}

Diff for: src/test/java/s0273.integer.to.english.words/SolutionTest.java

@@ -0,0 +1,13 @@
+package s0273.integer.to.english.words;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.Test;
+
+public class SolutionTest {
+    @Test
+    public void numberToWords() {
+        assertThat(new Solution().numberToWords(123), equalTo("One Hundred Twenty Three"));
+    }
+}