Problem:
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?
思路：
Solution (C++):
bool isSubsequence(string s, string t) {
int m = s.length(), n = t.length(), i = 0, j, temp = 0;
for (i; i < m; ++i) {
for (j = temp; j < n; ++j) {
if (t[j] == s[i]) { temp = j + 1; break; }
}
if (j == n) return false;
}
return true;
}
性能：
Runtime: 60 ms Memory Usage: 15.1 MB
思路：
Solution (C++):
性能：
Runtime: ms Memory Usage: MB
