【HDOJ】2424 Gary's Calculator

 1 import java.util.Scanner;
 2 import java.math.BigInteger;
 3 
 4 public class Main {
 5     public static void main(String[] args) {
 6         Scanner cin = new Scanner(System.in);
 7         int n;
 8         int i, j, k, tmp;
 9         int top;
10         boolean flag;
11         int t = 0;
12         while (cin.hasNext()) {
13             n = cin.nextInt();
14             for (i=0; i<n; ++i)
15                 buf[i] = cin.next();
16             flag = true;
17             if ((n&1) == 0)
18                 flag = false;
19             for (i=0; flag&&i<n; ++i) {
20                 if ((i & 1) == 1) {
21                     if (buf[i].charAt(0)!=‘+‘ && buf[i].charAt(0)!=‘*‘)
22                         flag = false;
23                 } else {
24                     if (buf[i].charAt(0)==‘+‘ || buf[i].charAt(0)==‘*‘)
25                         flag = false;
26                 }
27             }
28             System.out.printf("Case %d: ", ++t);
29             if (flag==false || n==0) {
30                 System.out.println("Invalid Expression!");
31                 continue;
32             }
33             top = 0;
34             bi[top++] = new BigInteger(buf[0]);
35             i = 1;
36             while (i < n) {
37                 if (buf[i].charAt(0) == ‘*‘) {
38                     BigInteger a = bi[top-1];
39                     BigInteger b = new BigInteger(buf[i+1]);
40                     bi[top-1] = a.multiply(b);
41                 } else {
42                     bi[top++] = new BigInteger(buf[i+1]);
43                 }
44                 i += 2;
45             }
46             BigInteger sum = BigInteger.ZERO;
47             for (i=0; i<top; ++i) {
48                 sum = sum.add(bi[i]);
49             }
50             System.out.println(sum.toString());
51         }
52     }
53     
54     final public static int MAXN = 25;
55     public static String[] buf = new String[MAXN];
56     public static BigInteger[] bi = new BigInteger[MAXN];
57 }