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### by Sumit Chourasia | Oct 03, 2020 | Category :coding | Tags : algorithmbinary-searchdata-structureeasyleetcode #### Is Subsequence - String - Easy - LeetCode

Given a string s and a string t, check if s is subsequence of t.

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).

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.

Example 1:

Input: s = "abc", t = "ahbgdc"
Output: true
Example 2:

Input: s = "axc", t = "ahbgdc"
Output: false

Constraints:

0 <= s.length <= 100
0 <= t.length <= 10^4
Both strings consists only of lowercase characters.

``````public class Solution {
public bool IsSubsequence(string s, string t) {
int i=0;
int j=0;
if(s.Length>t.Length){
IsSubsequence(t,s);
}
while(i<s.Length && j<t.Length){
if(s[i]==t[j]){
i++;
j++;
}
else{
j++;
}
}

return i==s.Length;
}

}``````

Time Complexity: O(n)

Space Complexity: O(1)