uva 10069 Distinct Subsequences dp + 大数

uva 10069 distinct Subsequences

题目大意：给出两个字符串A和B，找出A中所有与B相同的子字符串。

解题思路： if(A[j−1]==B[i−1]) {

dp[i][j]=dp[i][j]+dp[i−1][j−1];

}

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

/** * Created by spzn on 15-3-30. */
public class Main {
    public static void main(String args[]) {
        Scanner cin = new Scanner(system.in);
        BigInteger dp[][] = new BigInteger[105][10005];
        int T,n,m;
        String a,b;
        T = cin.nextInt();
        while (T-- > 0) {
            a = cin.next();
            b = cin.next();
            n = a.length();
            m = b.length();
            for (int i = 0; i <= n; i++) {
               dp[0][i] = BigInteger.ONE;
            }
            for (int i = 1; i <= m; i++) {
                dp[i][0] = BigInteger.ZERO;
                for (int j = 1; j <= n; j++) {
                    dp[i][j] = dp[i][j - 1];
                    if (a.charat(j - 1) == b.charat(i - 1)) {
                       dp[i][j] = dp[i][j].add(dp[i - 1][j - 1]);
                    }
                }
            }
            System.out.println(dp[m][n]);
        }
    }
}