【HDOJ】2424 Gary's Calculator

大数乘法加法，直接java A了。

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

public class Main {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        int n;
        int i, j, k, tmp;
        int top;
        boolean flag;
        int t = 0;
        while (cin.hasNext()) {
            n = cin.nextInt();
            for (i=0; i<n; ++i)
                buf[i] = cin.next();
            flag = true;
            if ((n&1) == 0)
                flag = false;
            for (i=0; flag&&i<n; ++i) {
                if ((i & 1) == 1) {
                    if (buf[i].charAt(0)!='+' && buf[i].charAt(0)!='*')
                        flag = false;
                } else {
                    if (buf[i].charAt(0)=='+' || buf[i].charAt(0)=='*')
                        flag = false;
                }
            }
            System.out.printf("Case %d: ", ++t);
            if (flag==false || n==0) {
                System.out.println("Invalid Expression!");
                continue;
            }
            top = 0;
            bi[top++] = new BigInteger(buf[0]);
            i = 1;
            while (i < n) {
                if (buf[i].charAt(0) == '*') {
                    BigInteger a = bi[top-1];
                    BigInteger b = new BigInteger(buf[i+1]);
                    bi[top-1] = a.multiply(b);
                } else {
                    bi[top++] = new BigInteger(buf[i+1]);
                }
                i += 2;
            }
            BigInteger sum = BigInteger.ZERO;
            for (i=0; i<top; ++i) {
                sum = sum.add(bi[i]);
            }
            System.out.println(sum.toString());
        }
    }
    
    final public static int MAXN = 25;
    public static String[] buf = new String[MAXN];
    public static BigInteger[] bi = new BigInteger[MAXN];
}