Google – String Decimal Add

Google – String Decimal Add
给两个string表示实数（带小数点，不是整数），做加法。
[Solution]
和整数一样的解法，分成两部分加就好了
[Note]
split "."的时候一定要转义。

  public String decimalAdd(String a, String b) {

    if (a == null || b == null) {

      return a == null? b : a;

    }

 

    String[] sp1 = a.split("\\.");

    String[] sp2 = b.split("\\.");

    int remainder = 0;

    int l = sp1.length > 1? sp1[1].length() - 1 : -1;

    int r = sp2.length > 1? sp2[1].length() - 1 : -1;

    StringBuilder sb = new StringBuilder();

    while (l >= 0 || r >= 0) {

      int d1 = l >= 0? sp1[1].charAt(l) - '0' : 0;

      int d2 = r >= 0? sp2[1].charAt(r) - '0' : 0;

      int sum = d1 + d2 + remainder;

      if (sum >= 10) {

        sum -= 10;

        remainder = 1;

      }

      else {

        remainder = 0;

      }

      sb.append(sum);

      l--;

      r--;

    }

 

    if (sp1.length > 1 || sp2.length > 1) {

      sb.append(".");

    }

 

    l = sp1[0].length() - 1;

    r = sp2[0].length() - 1;

    while (l >= 0 || r >= 0) {

      int d1 = l >= 0? sp1[0].charAt(l) - '0' : 0;

      int d2 = r >= 0? sp2[0].charAt(r) - '0' : 0;

      int sum = d1 + d2 + remainder;

      if (sum >= 10) {

        sum -= 10;

        remainder = 1;

      }

      else {

        remainder = 0;

      }

      sb.append(sum);

      l--;

      r--;

    }

    if (remainder != 0) {

      sb.append(remainder);

    }

 

    return sb.reverse().toString();

  }

Read full article from Google – String Decimal Add