【HDOJ】1314 Numerically Speaking

学了几天的Java了，终于独立A了一道大数计算。感觉还得练Java啊。

import java.util.Scanner;
import java.math.BigInteger;
import java.lang.StringBuilder;

public class Main {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        while (cin.hasNextLine()) {
            String line = cin.nextLine();
            char l0 = line.charAt(0);
            if (l0 == '*')
                break;
            if (l0>='0' && l0<='9') {
                StringBuilder builder = new StringBuilder();
                BigInteger x = new BigInteger(line);
                BigInteger div = new BigInteger("26");
                BigInteger[] vals = new BigInteger[2];
                while (x.compareTo(BigInteger.ZERO) != 0) {
                    vals = x.divideAndRemainder(div);
                    char ch = (char)(vals[1].intValue()+96);
                    builder.append(ch);
                    x = vals[0];
                }
                builder.reverse();
                String ans = new String(builder.toString());
                System.out.print(ans);
                int l = ans.length();
                while (l < WIDTH) {
                    System.out.print(' ');
                    ++l;
                }
            } else {
                int length = line.length();
                System.out.print(line);
                int l = length;
                while (l < WIDTH) {
                    System.out.print(' ');
                    ++l;
                }
                BigInteger div = new BigInteger("26");
                BigInteger sum = new BigInteger(String.valueOf((int)(line.charAt(length-1))-96));
                for (int i=length-2; i>=0; --i) {
                    // System.out.print("current sum = ");
                    // System.out.println(sum.toString());
                    BigInteger tmp = div.multiply(new BigInteger(String.valueOf((int)(line.charAt(i))-96)));
                    sum = sum.add(tmp);
                    div = div.multiply(new BigInteger("26"));
                }
                line = new String(sum.toString());
            }
            int length = line.length();
            int x = length%3;
            x = (x==0) ? 3:x;
            int j = 0;
            for (int i=0; i<length; ++i) {
                if (i < x) {
                    System.out.print(line.charAt(i));
                } else {
                    if ((j+1)<length && (j%3)==0) {
                        System.out.print(',');
                    }
                    ++j;
                    System.out.print(line.charAt(i));
                }
            }
            System.out.println();
        }
    }
    public static void reverse(byte[] bytes, int l) {
        byte tmp;
        for (int i=0; i+i<l; ++i) {
            tmp = bytes[i];
            bytes[i] = bytes[l-1-i];
            bytes[l-1-i] = tmp;
        }
    }
    static final int WIDTH = 22;
}