273 - Integer to English Words

JAVA

• class Solution {
      private static Map<Integer, String> map;
  
      static {
          map = new HashMap<>();
          map.put(1, "One");
          map.put(2, "Two");
          map.put(3, "Three");
          map.put(4, "Four");
          map.put(5, "Five");
          map.put(6, "Six");
          map.put(7, "Seven");
          map.put(8, "Eight");
          map.put(9, "Nine");
          map.put(10, "Ten");
          map.put(11, "Eleven");
          map.put(12, "Twelve");
          map.put(13, "Thirteen");
          map.put(14, "Fourteen");
          map.put(15, "Fifteen");
          map.put(16, "Sixteen");
          map.put(17, "Seventeen");
          map.put(18, "Eighteen");
          map.put(19, "Nineteen");
          map.put(20, "Twenty");
          map.put(30, "Thirty");
          map.put(40, "Forty");
          map.put(50, "Fifty");
          map.put(60, "Sixty");
          map.put(70, "Seventy");
          map.put(80, "Eighty");
          map.put(90, "Ninety");
          map.put(100, "Hundred");
          map.put(1000, "Thousand");
          map.put(1000000, "Million");
          map.put(1000000000, "Billion");
      }
  
      public String numberToWords(int num) {
          if (num == 0) {
              return "Zero";
          }
          StringBuilder sb = new StringBuilder();
          for (int i = 1000000000; i >= 1000; i /= 1000) {
              if (num >= i) {
                  sb.append(get3Digits(num / i)).append(' ').append(map.get(i));
                  num %= i;
              }
          }
          if (num > 0) {
              sb.append(get3Digits(num));
          }
          return sb.substring(1);
      }
  
      private String get3Digits(int num) {
          StringBuilder sb = new StringBuilder();
          if (num >= 100) {
              sb.append(' ').append(map.get(num / 100)).append(' ').append(map.get(100));
              num %= 100;
          }
          if (num > 0) {
              if (num < 20 || num % 10 == 0) {
                  sb.append(' ').append(map.get(num));
              } else {
                  sb.append(' ').append(map.get(num / 10 * 10)).append(' ').append(map.get(num % 10));
              }
          }
          return sb.toString();
      }
  }
  

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