HDU4927 Series 1 高精度

 1 import java.math.BigInteger;
 2 import java.util.Scanner;
 3 import java.io.*;
 4 
 5 public class Main {
 6     public static void main(String[] args) {
 7         Scanner cin = new Scanner(System.in);
 8             int t,n;
 9             BigInteger[] a = new BigInteger[3004];
10             BigInteger[] b = new BigInteger[3004];
11         //    BigInteger[][] c = new BigInteger[3004][1500];
12             b[0] = BigInteger.valueOf(1);
13             t=cin.nextInt();
14             while(t > 0)
15             {
16               t--;
17               BigInteger  ans = BigInteger.valueOf(0);
18               n = cin.nextInt();
19               for(int i = 1;i <= n-1;i ++)
20               {
21                   b[i] = b[i-1].multiply(BigInteger.valueOf(n-i));
22                   b[i] = b[i].divide(BigInteger.valueOf(i));
23               }
24               int j = 0;
25               if(n % 2 == 0)
26                   j = 1;
27               for(int i = 1;i <= n;i ++,j++)
28               {
29                  a[i] = cin.nextBigInteger();
30                 //a[i].multiply(b[n-1].divide(b[i-1].multiply(b[n-i])));
31                  a[i] = a[i].multiply(b[i-1]);
32                  if(j % 2 == 0 )
33                    ans = ans.add(a[i]);
34                  else ans = ans.subtract(a[i]);
35                 // System.out.println(a[i]);
36               
37             }
38           System.out.println(ans); 
39         }
40     }
41 }