题目：

题解：

bool isSubsequence(char* s, char* t) {
    int n = strlen(s), m = strlen(t);

    int f[m + 1][26];
    memset(f, 0, sizeof(f));
    for (int i = 0; i < 26; i++) {
        f[m][i] = m;
    }

    for (int i = m - 1; i >= 0; i--) {
        for (int j = 0; j < 26; j++) {
            if (t[i] == j + 'a')
                f[i][j] = i;
            else
                f[i][j] = f[i + 1][j];
        }
    }
    int add = 0;
    for (int i = 0; i < n; i++) {
        if (f[add][s[i] - 'a'] == m) {
            return false;
        }
        add = f[add][s[i] - 'a'] + 1;
    }
    return true;
}