题目：

题解：

class Solution {
public:bool isSubsequence(string s, string t) {int n = s.size(), m = t.size();vector<vector<int> > f(m + 1, vector<int>(26, 0));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;elsef[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;}
};