Is Subsequence
Question
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?
Answer
贪心算法求解即可
class Solution {
public:
bool isSubsequence(string s, string t) {
int index = 0;
if (s.size() == 0) return true;
for (auto ch : t) {
if (s[index] == ch) {
index++;
}
if (index == s.size()) return true;
}
return false;
}
};
