leetcode刷题系列：392. Is Subsequence

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?
Credits:

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

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class Solution {
public:
bool isSubsequence(string s, string t) {
int lens = s.size();
int lent = t.size();
if(lens > lent)
return false;
int start = 0;
int j = 0;
for(int i = 0; i < lens; ++i)
{
for(; j < lent;j++)
{
if(s[i] == t[j])
{
if(j == lent - 1 && i != lens - 1)
return false;
j++;
break;
}
else
{
if(  j == lent - 1 )
return false;
continue;
}
}
}
return true;
}
};