title
Given a string s and a string t, check if s is subsequence of t.
You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).
A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (ie, “ace” is a subsequence of “abcde” while “aec” is not).
Example 1:
s = "abc", t = "ahbgdc"
Return true.
Example 2:
s = "axc", t = "ahbgdc"
Return false.
Follow up:
If there are lots of incoming S, say S1, S2, … , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?
solution
判断是否子串，可以维护nextPost[i][j] 表示当前i之后的最近字符j的位置
class Solution {
public:
bool isSubsequence(string s, string t) {
int b = 0;
for (int i = 0; i < t.length(); i++) {
if (b < s.length() && t[i] == s[b]) {
b++;
}
}
return b == s.length();
}
};