POJ 1220 NUMBER BASE CONVERSION(进制转换，大数)

输入输入如题面，注意对0的处理，然后Java大数真好用。

import java.math.BigInteger;
import java.util.Arrays;
import java.util.*;
import java.io.*;

public class Main{
    static int valOfChar(char a){
        if(a>='0'&&a<='9')return a-'0';
        else if(a>='A'&&a<='Z')return a-'A'+10;
        else return a-'a'+36;
    }
    static char valOfInt(int a){
        if(a<10)return (char)(a+'0');
        else if(a<36)return (char)(a-10+'A');
        else return (char)(a-36+'a');
    }
    static int valOfSt(String a){
        int ans = 0;
        for(int i = 0 ; i < a.length() ; ++i){
            ans = ans*10+a.charAt(i)-'0';
        }
        return ans;
    }
    public static void main(String args[]) {
        int T;
        Scanner cin = new Scanner(System.in);
        String in;
        BigInteger res;
        T = cin.nextInt();
        BigInteger A,B;
        int a,b;
        while (T--!=0){
            res = BigInteger.valueOf(0);
            a = cin.nextInt();
            A = BigInteger.valueOf(a);
            b = cin.nextInt();
            B = BigInteger.valueOf(b);
            in = cin.next();
            for(int i = 0 ; i < in.length() ; ++i){
                res = res.multiply(A).add(BigInteger.valueOf(valOfChar(in.charAt(i))));
            }
            Stack<Character>deal = new Stack<Character>();
            while (res.compareTo(BigInteger.ZERO)>0){
                deal.push(valOfInt(valOfSt(res.mod(B).toString())));
                res = res.divide(B);
            }
            System.out.println(a+" "+in);
            System.out.print(b+" ");
            if(deal.empty())System.out.print(0);
            while (!deal.empty())System.out.print(deal.pop());
            System.out.println('\n');
        }
    }
}

总之，难受。。