hdu 5282 序列计数

// 统计 s1 的子序列中是 s1 和 s2 的最长公共子序列的个数

#include "bits/stdc++.h"
using namespace std;
int T;
char s1[1010], s2[1010];
int dp[1010][1010];
long long Count[1010][1010];
const long long MOD = 1000000007;

int main()
{
    int len1, len2;
    scanf("%d", &T);
    while(T--) {
        memset(dp, 0, sizeof(dp));
        memset(Count, 0, sizeof(Count));
        scanf("%s", s1 + 1);
        scanf("%s", s2 + 1);
        len1 = strlen(s1 + 1);
        len2 = strlen(s2 + 1);
        int i, j;

        for(i = 0; i <= len1; ++i) {
            Count[i][0] = 1;
        }
        for(j = 0; j <= len2; ++j) {
            Count[0][j] = 1;
        }

        for(i = 1; i <= len1; ++i) {
            int k = 0, p = 0;
            for(j = 1; j <= len2; ++j) {
//                printf("%d %d
", i, j);
//                if(s1[i] == s2[j]) {
//                    dp[i][j] = dp[i - 1][k] + 1;
//                }
//                else {
//                    dp[i][j] = dp[i - 1][j];
//                }
//                if(dp[i - 1][k] < dp[i - 1][j]) {
//                    k = j;
//                }
                if(s1[i] == s2[j]) {
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                }
                else {
                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
                }

                if(s1[i] == s2[j]) {
                    p = j;
                }
                if(dp[i][j] == dp[i - 1][p - 1] + 1) {
                    Count[i][j] += Count[i - 1][p - 1];
                }
                if(dp[i][j] == dp[i - 1][j]) {
                    Count[i][j] += Count[i - 1][j];
                }
                Count[i][j] %= MOD;
            }
        }
        printf("%lld
", Count[len1][len2]);
    }
}