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"

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?

Credits:
Special thanks to @pbrother for adding this problem and creating all test cases.

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解法：題目很簡單，判斷字串是否為另一字串的子串，只需遍歷一遍即可，程式碼如下：

#include<iostream>
#include<string>
using namespace std;
bool isSubsequence(string s, string t) 
{
       int lenS=s.length(); 
       int lenT=t.length();
       int i=0,j=0;
       while(i<lenS&&j<lenT)
       {
       		if(s[i]==t[j])
       		{
       			i++;
       			j++;
       		}
       		else
       			j++;
       }
       return i==lenS;
}
int main()
{
	cout<<isSubsequence("sh","sje")<<endl;
}